,,the ,,preparation ,,mounting ,,of ,,microscopic ,,objects4 ,,by ,,thomas ,,davies4 ,,london3 ,,robert ,,hardwicke1 #aib1 ,,piccadilly4 ,,and ,,all ,,booksellers4 ,a ,new ,edition1 ,revised and ,enlarged4 ,price #bs4 #f;d4 plain2 #ds4 coloured4 ,,half-,,hours ,,with ,,the ,,microscope4 ,a ,popular ,guide to the ,use of the ,microscope as a ,means of ,amusement and ,instruction4 ,with ,drawings of #bej objects from ,nature1 by ,,tuffen ,,west4 ,by ,e4 ,,lankester1 ,m4,d41 ,f4,r4,s4 ,,contents3 ,half an hour on the ,structure4 ,half an hour in the ,garden4 ,half an hour in the ,country4 ,half an hour at the ,pondside4 ,half an hour at the ,seaside4 ,half an hour ,indoors4 ,appendix3 the ,preparation and ,mounting of ,objects4 ,fcp4 #hvo41 #fs4 beautifully illustrated by hand-painting4 ,,rust1 ,,smut1 ,,mildew1 ,,and ,,mould under the ,,microscope3 a ,plain and ,easy ,guide to the ,study of ,microscopic ,fungi4 ,by ,m4 ,c4 ,,cooke4 ,coloured ,plates of over #cjj ,figures4 ,london3 ,,robert ,,hardwicke1 #aib1 ,piccadilly2 and all ,booksellers4 ,,preface4 ,in bringing this ,handbook before the public1 the ,author believes that he is supplying a want which has been long felt4 ,much information concerning the 8,preparation and ,mounting of ,microscopic ,objects0 has been already published2 but mostly as supplementary chapters only1 in books written professedly upon the ,microscope4 ,from this it is evident that it was necessary to consult a number of works in order to obtain anything like a complete knowledge of the subject4 ,these pages1 however1 will be found to comprise all the most approved methods of mounting1 together with the results of the ,author's experience1 and that of many of his friends1 in every department of microscopic manipulation2 and as it is intended to assist the beginner as well as the advanced student1 the very rudiments of the art have not been omitted4 ,as there is a diversity of opinion as to the best mode of proceeding in certain cases1 numerous quotations have been made4 ,wherever this has been done1 the ,author believes that he has acknowledged the source from which he has taken the information2 and he here tenders his sincere thanks to those friends who so freely allowed him to make use of their works4 ,should1 however1 anyone find his own process in these pages unacknowledged1 the author can only plead oversight1 and his regret that such should have been the case4 ,,contents ,,page ,,preface iii ,,chapter ,i4 ,,apparatus4 #a ,,chapter ,,ii4 ,,to ,,prepare ,,and ,,mount ,,objects 8,,dry40 #bb ,,chapter ,,iii4 ,,mounting ,,in ,,canada ,,balsam4 #ef ,,chapter ,,iv4 ,,preservative ,,liquids1 ,,etc41 ,,particularly ,,where ,,cells ,,are ,,used4 #hc ,,chapter ,v4 ,,sections ,,and ,,how ,,to ,,cut ,,them1 ,,with ,,some ,,remarks ,,on ,,dissection4 #if ,,chapter ,,vi4 ,,injection4 #abb ,,chapter ,,vii4 ,,miscellaneous4 #adj ,,index4 #aec ,,the ,,preparation ,,and ,,mounting ,,of ,,microscopic ,,objects4 ,,chapter ,i4 ,,apparatus4 ,before entering into the subject of the setting of ,objects for the ,microscope1 the student must be convinced of the necessity of cleanliness in everything relating to the use of that instrument4 ,in no branch is this more apparent than in the preparation of objects2 because a slide which would be considered perfectly clean when viewed in the ordinary way is seen to be far otherwise when magnified some hundreds of diameters2 and those constant enemies1 the floating particles of dust1 are everywhere present1 and it is only by unpleasant experience that we fully learn what cleanliness is4 ,any object which is to be viewed under the microscope must1 of course1 be supported in some way--this is now usually done by placing it upon a glass slide1 which on account of the transparency has a great advantage over other substances4 ,these 8slides0 are almost always made of one size1 viz41 three inches long by one broad1 generally having the edges ground so as to remove all danger of scratching or cutting any object with which they may come in contact4 ,the glass must be very good1 else the surface will always present the appearance of uncleanliness and dust4 ,this dusty look is very common amongst the cheaper kinds of slides1 because they are usually 8sheet0 glass2 but is seldom found in those of the quality known amongst dealers by the name of 8patent plate40 ,this latter is more expensive at first1 but in the end there is little difference in the cost1 as so many of the cheaper slides cannot be used for delicate work if the mounted object is to be seen in perfection4 ,these slides vary considerably in thickness2 care should1 therefore1 be taken to sort them1 so that the more delicate objects with which the higher powers are to be used maybe mounted upon the thinnest1 as the light employed in the illumination is then less interfered with4 ,to aid the microscopist in this work1 a metal circle may be procured1 having a number of different sized openings on the outer edge1 by which the glass slides can be measured4 ,these openings are numbered1 and the slides may be separated according to these numbers2 so that when mounting any object there will be no need of a long search for that glass which is best suited to it4 ,when fresh from the dealer's hands1 these slides are generally covered with dust1 c41 which may be removed by well washing in clean rain-water2 but if the impurity is obstinate1 a little washing soda may be added1 care being taken1 however1 that every trace of this is removed by subsequent waters1 otherwise the crystals will afterwards form upon the surface4 ,a clean linen cloth should be used to dry the slides1 after which they may be laid by for use4 ,immediately1 however1 before being used for the reception of objects by any of the following processes1 all dust must be removed by rubbing the surface with clean wash-leather or a piece of cambric1 and1 if needful1 breathing upon it1 and then using the leather or cambric until perfectly dry4 ,any small particles left upon the surface may generally be removed by blowing gently upon it1 taking care to allow no damp to remain4 ,we have before said1 that any object to be viewed in the microscope must have its support2 but if this object is to be preserved1 care must be taken that it is defended from the dust and other impurities4 ,for this purpose it is necessary to use some transparent cover1 the most usual at one time being a plate of mica1 on account of its thinness2 this substance is now1 however1 never used1 thin glass being substituted1 which answers admirably4 ,sometimes it is required to 8take up0 as little space as possible1 owing to the shortness of focus of the object-glasses4 ,it can be procured of any thickness1 from one-fiftieth to one-two-hundred-and-fiftieth of an inch4 ,on account of its want of strength it is difficult to cut1 as it is very liable to 8fly0 from the point of the diamond4 ,to overcome this tendency as much as possible1 it must be laid upon a thicker piece1 previously made wet with water1 which causes the thin glass to adhere more firmly1 and consequently to bear the pressure required in cutting the covers4 ,the process of cutting being so difficult1 especially with the thinner kinds1 little or nothing is gained by cutting those which can be got from the dealers1 as the loss and breakage is necessarily greater in the hands of an amateur4 ,it is convenient1 however1 to have on hand a few larger pieces1 from which unusual sizes may be cut when required4 ,if the pieces required are rectangular1 no other apparatus will be required save a diamond and a flat rule2 but if circles are wanted1 a machine for that purpose should be used 7of which no description is necessary here74 ,there are1 however1 other contrivances which answer tolerably well4 ,one method is1 to cut out from a thick piece of cardboard a circle rather larger than the size wanted4 ,dr4 ,carpenter recommends metal rings with a piece of wire soldered on either side2 and this1 perhaps1 is the best1 as cardboard is apt to become rough at the edge when much used4 ,a friend of mine uses thin brass plates with circles of various sizes 8turned0 through them1 and a small raised handle placed at one end4 ,the diamond must be passed round the inner edge1 and so managed as to meet again in the same line1 in order that the circle may be true1 after which they may be readily disengaged4 ,the sizes usually kept in stock by the dealers are one-half1 five-eighths1 and three-quarters inch diameter2 but other sizes may be had to order4 ,for the information of the beginner it may be mentioned here that the price of the circles is a little more than of the squares2 but this is modified in some degree by the circle being rather lighter4 ,if appearance1 however1 is cared for at all1 the circles look much neater upon the slides when not covered with the ornamental papers2 but if these last are used 7as will shortly be described7 the squares are equally serviceable4 ,as before mentioned1 the thin glass is made of various thicknesses1 and the beginner will wish to know which to use4 ,for objects requiring no higher power than the one-inch object-glass1 the thicker kinds serve well enough2 for the half-inch the medium thickness will be required2 while1 for higher powers1 the thinnest covers must be used4 ,the 8test-objects0 for the highest powers require to be brought so near to the object-glass that they admit of the very thinnest covering only1 and are usually mounted betwixt glasses which a beginner would not be able to use without frequent breakage2 but if these objects were mounted with the common covers1 they would be really worthless with the powers which they require to show them satisfactorily4 ,it may be desirable to know how such small differences as those betwixt the various thin glass covers can be measured4 ,for this purpose there are two or three sorts of apparatus1 all1 however1 depending upon the same principle4 ,the description of one1 therefore1 will be sufficient4 ,upon a small stand is a short metal lever 7as it may be termed7 which returns by a spring to one certain position1 where it is in contact with a fixed piece of metal4 ,at the other end this lever is connected with a 8finger10 which moves round a dial like that of a watch1 whereupon are figures at fixed distances4 ,when the lever is separated from the metal which is stationary1 the other end being connected with the 8finger0 of the dial1 that 8finger0 is moved in proportion to the distance of the separation4 ,the thin glass is1 therefore1 thrust betwixt the end of the lever and fixed metal1 and each piece is measured by the figures on the dial in stated and accurate degrees4 ,this kind of apparatus1 however1 is expensive1 and when not at our command1 the thin glass may be placed edgewise in the stage forceps1 and measured very accurately with the micrometer4 ,cleanliness with the thin glass is1 perhaps1 more necessary than with the slides1 especially when covering objects which are to be used with a high power2 but it is far more difficult to attain1 on account of the liability to breakage4 ,the usual method of cleaning these covers is as follows3--,two discs of wood1 about two inches in diameter1 are procured1 one side of each being perfectly flat and covered with clean wash-leather4 ,to the other side of these a small knob is firmly affixed as a handle1 or where practicable the whole may be made out of a solid piece4 ,in cleaning thin glass1 it should be placed betwixt the covered sides of the discs1 and may then be safely rubbed with a sufficient pressure1 and so cleaned on both sides by the leather4 ,if1 however1 the glass be greasy1 as is sometimes the case1 it must be first washed with a strong solution of potash1 infusion of nut-galls1 or any of the commonly used grease-removing liquids2 and with some impurities water1 with the addition of a few drops of strong acid1 will be found very useful1 but this last is not often required4 ,the above method of cleaning thin glass should always be used by beginners2 but after some experience the hand becomes so sensitive that the above apparatus is often dispensed with1 and the glasses1 however thin1 may be safely cleaned betwixt the fingers and thumb with a cambric handkerchief1 having first slightly damped the ends of the fingers employed to obtain firm hold4 ,when the dirt is very obstinate1 breathing upon the glass greatly facilitates its removal1 and the sense of touch becomes so delicate that the breakage is inconsiderable2 but this method cannot be recommended to novices1 as nothing but time spent in delicate manipulation can give the sensitiveness required4 ,it was before mentioned that the ordinary glass slides were sometimes worthless1 especially for fine objects1 from having a rough surface1 which presented a dusty appearance under the microscope4 ,this imperfection exists in some thin glass also1 and it is irremediable2 so that it is useless to attempt to cleanse it2 nevertheless1 care should be taken not to mistake dirty glass for this roughness1 lest good glass be laid aside for a fault which does not really belong to it4 ,when any object which it is desired to mount is of considerable thickness1 or will not bear pressure1 it is evident that a wall must be raised around it to support the thin glass--this is usually termed a 8cell40 ,there are various descriptions of these1 according to the class of objects they are required to protect2 and here may be given a description of those which are most generally used in mounting 8dry0 objects1 leaving those required for the preservation of liquids until we come to the consideration of that mode of mounting4 ,many have made use of the following slides4 ,two pieces of hard wood of the usual size 7#c in4 by #a in471 not exceeding one-sixteenth of an inch in thickness1 are taken1 and a hole is then drilled in the middle of one of these of the size required4 ,the two pieces are then united by glue or other cement1 and left under pressure until thoroughly dry1 when the cell is fit for use4 ,others substitute cardboard for the lower piece of wood1 which is less tedious1 and is strong enough for every purpose4 ,this class of 8cell0 is1 of course1 fitted for opaque objects only where no light is required from below2 and as almost all such are better seen when on a dark background1 it is usual to fix a small piece of black paper at the bottom of the cell upon which to place them4 ,for very small objects the 8grain0 which all such paper has when magnified detracts a little from the merit of this background2 and lately ,i have used a small piece of thin glass covered on the back with black varnish1 and placed the object upon the smooth untouched side4 ,another method of making these cells is as follows3--,two 8punches10 similar to those used for cutting 8gun-wads10 are procured1 of such sizes that with the smaller may be cut out the centre of the larger1 leaving a ring whose side is not less than one-eighth of an inch wide4 ,these rings may be readily made1 the only difficulty being to keep the sides parallel2 but a little care will make this easy enough4 ,for this purpose close-grained cardboard may be conveniently used4 ,it must have a well-glazed surface1 else the varnish or cement used in affixing the thin glass cover sinks into the substance1 and the adherence is very imperfect4 ,when this takes place it is easily remedied by brushing over the surface of the cardboard a strong solution of gum or isinglass2 and this application1 perhaps1 closes also the pores of the card1 and so serves a double purpose4 ,but1 of course1 the gum must be perfectly dried before the ring is used4 ,for cardboard1 gutta-percha has been substituted1 but cannot be recommended1 as it always becomes brittle after a certain time1 never adheres to the glass with the required firmness1 and its shape is altered when worked with even a little heat4 ,leather is often used1 and is very convenient2 it should be chosen1 however1 of a close texture1 and free from oil1 grease1 and all those substances which are laid upon it by the 8dressers40 ,rings of cardboard1 c41 have been rejected by persons of great experience1 because they are of such a nature that dampness can penetrate them4 ,this fault can be almost1 if not totally1 removed by immersing them in some strong varnish1 such as the asphalt varnish hereinafter mentioned2 but they must be left long enough when affixed to the glass slide to become perfectly dry1 and this will require a much longer time than at first would be supposed4 ,there has1 however1 been lately brought out what is termed the ivory cell4 ,this is a ring of ivory-like substance1 which may be easily and firmly fixed to the glass slide by any of the commonly-used cements1 and so forms a beautiful cell for any dry objects4 ,they are made of different sizes1 and are not expensive4 ,sometimes slides are used which are made by taking a thin slip of wood of the usual size 7#c in4 by #a in471 in the centre of which is cut a circular hole large enough to receive the object4 ,a piece of thin glass is fixed underneath the slide1 forming a cell for the object1 which may then be covered and finished like an ordinary slide4 ,this has the advantage of serving for transparent objects for which the before-mentioned wooden slides are unsuitable4 ,a slight modification of this plan is often used where the thickness of the objects is inconsiderable1 especially with some of the ,diatomace1 often termed 8test-objects40 ,the wooden slide is cut with the central opening as above1 and two pieces of thin glass are laid upon it1 betwixt which the diatoms or other objects are placed1 and kept in their proper position by a paper cover4 ,this arrangement is a good one1 insomuch as the very small portion of glass through which the light passes on its way to the microscope from the reflector causes the refraction or interference to be reduced to the lowest point4 ,a novice would naturally think the appearance of some of the slides above mentioned very slovenly and unfinished2 but they are often covered with ornamental papers1 which may be procured at almost every optician's1 at a cost little more than nominal1 and of innumerable patterns and colours4 ,how to use these will be described in another place4 ,it is very probable that a beginner would ask his friend what kind of slides he would advise him to use4 ,almost all those made of wood are liable to warp more or less1 even when the two pieces are separate or of different kinds2 those of cardboard and wood are generally free from this fault1 yet the slides1 being opaque1 prevent the employment of the ,lieberkuhn4 ,to some extent glass slides1 when covered with ornamental papers1 are liable to the same objection1 as the light is partly hindered4 ,and sometimes the dampness from the paste1 or other substance used to affix the papers1 penetrates to the object1 and so spoils it1 though this may be rendered less frequent by first attaching the thin glass to the slide by some harder cement4 ,much time1 however1 is taken up by the labour of covering the slides1 which is a matter of consideration with some4 ,certainly1 the cost of the glass slides was formerly great2 but now they are reasonable enough in this respect1 so that this objection is removed4 ,it is1 therefore1 well to use glass slides1 except where the thin glasses are employed for tests1 c41 as above4 ,when the thin glass circles are placed upon the slides1 and the edge is varnished with black or coloured rings1 the appearance of finish is perfect4 ,the trouble is much less than with most of the other methods1 and the illumination of the object very slightly interfered with4 ,to varnish the edges of these covers1 make circles of any liquid upon the glass slide1 and perform any other 8circular0 work mentioned hereafter1 the little instrument known as 8,shadbolt's turntable0 is almost indispensable4 ,it is made as follows3--,at one end of a small piece of hard wood is fixed an iron pivot about one-eighth inch thick1 projecting half an inch from the wood1 which serves as a centre upon which a round brass table three inches in diameter revolves4 ,on the surface of this are two springs1 about one and a half inches apart1 under which the slide is forced and so kept in position1 whilst the central part is left open to be worked upon4 ,the centre is marked1 and two circles half an inch and one inch in diameter are usually deeply engraved upon the table to serve as guides in placing the slide1 that the ring may be drawn in the right position4 ,when the slide is placed upon the 8table0 underneath the springs1 a camel-hair pencil is filled with the varnish1 or other medium used1 and applied to the surface of the glass2 the table is then made to revolve1 and a circle is consequently produced1 the diameter of which it is easy to regulate4 ,many objects for the microscope may be seriously injured by allowing the fingers to touch them--many more are so minute that they cannot be removed in this way at all1 and often it is necessary to take from a mass of small grains1 as in sand1 some particular particle4 ,to accomplish this1 there are two or three contrivances recommended3 one by means of split bristles1 many of which will readily be found in any shaving brush when it has been well used4 ,the bristles when pressed upon any hard surface open1 and when the pressure is removed close again with a spring2 but the use of these is limited4 ,camel-hair pencils are of great service for this and many other purposes to the microscopist4 ,in very fine work they are sometimes required so small that all the hairs with the exception of one or two finer pointed ones are removed4 ,a few of various sizes should always be kept on hand4 ,equally necessary are fine pointed needles4 ,they are very readily put up for use by thrusting the 8eye0 end into a common penholder1 so as to be firm4 ,the points may be readily renewed1 when injured1 on a common whetstone2 but when out of use they may be protected by being thrust into a piece of cork4 ,knives of various kinds are required in some branches of microscopic work1 but these will be described where 8dissection10 c41 is treated at some length1 as also various forms of scissors4 ,in the most simple objects1 however1 scissors of the usual kind are necessary4 ,two or three sizes should always be kept at hand1 sharp and in good order4 ,a set of glass tubes1 kept in a case of some sort to prevent breakage1 should form part of our 8fittings0 and be always cleaned immediately after use4 ,these are generally from six to ten inches long and from one-eighth to a quarter of an inch in diameter4 ,one of these should be straight and equal in width at both ends2 one should be drawn out gradually to a fine point2 another should be pointed as the last1 but be slightly curved at the compressed end1 in order to reach points otherwise unattainable4 ,it is well to have these tubes of various widths at the points1 as in some waters the finer would be inevitably stopped4 ,for other purposes the fine ones are very useful1 especially in the transfer of 8preservative liquids0 which will come under notice in another chapter4 ,forceps are required in almost all microscopic manipulations1 and consequently are scarcely ever omitted from the microscopic box1 even the most meagrely furnished2 but of these there are various modifications1 which for certain purposes are more convenient than the usual form4 ,the ordinary metal ones are employed for taking up small objects1 thin glass1 c42 but when slides are to be held over a lamp1 or in any position where the fingers cannot conveniently be used1 a different instrument must be found4 ,of these there are many kinds2 but ,mr4 ,page's wooden forceps serve the purpose very well4 ,two pieces of elastic wood are strongly bound together at one end1 so that they may be easily opened at the other1 closing again by their own elasticity4 ,through the first of these pieces is loosely passed a brass stud1 resembling a small screw1 and fastened in the second1 and through the second a similar stud is taken and fixed in the first--so that on pressure of the studs the two strips of wood are opened to admit a slide or other object required to be held in position4 ,the wood strips are generally used three or four inches long1 one inch wide1 and about one-eighth inch thick4 ,again1 some objects when placed upon the glass slide are of such an elastic nature that no cement will secure the thin glass covering until it becomes hard4 ,this difficulty may be overcome by various methods4 ,the following are as good and simple as any4 ,take two pieces of wood about two inches long1 three-quarters wide1 and one-quarter thick2 and a small rounded piece one inch long and one-quarter in diameter2 place this latter betwixt the two larger pieces4 ,over one end of the two combined pass an india-rubber band4 ,this will give a continual pressure1 and may be opened by bringing the two pieces together at the other end2 the pressure may be readily made uniform by paring the points at the inner sides1 and may be regulated by the strength of the india-rubber band4 ,these bands may be made cheaply1 and of any power1 by procuring a piece of india-rubber tubing of the width required1 and cutting off certain breadths4 ,another very simple method of getting this pressure is mentioned in the 8,micrographic ,dictionary40 ,two pieces of whalebone of the length required are tied together firmly at each end4 ,it is evident that any object placed betwixt them will be subject to continual pressure4 ,the power of this may be regulated by the thickness and length of the whalebone4 ,this simple contrivance is very useful4 ,common watch-glasses should always be kept at hand4 ,they are certainly the cheapest1 and their transparency makes them very convenient reservoirs in which objects may be steeped in any liquid2 as it saves much trouble to examine cursorily under the microscope1 when the air-bubbles are expelled from insects1 c41 c4 ,they are readily cleaned1 and serve very well as covers1 when turned upside down1 to protect any objects from the dust4 ,for this latter purpose ,dr4 ,carpenter recommends the use of a number of bell-glasses1 especially when one object must be left for a time 7which often happens7 in order that another may be proceeded with4 ,wine glasses1 when the 8legs0 are broken1 may thus be rendered very useful4 ,as heat is necessary in mounting many objects1 a lamp will be required4 ,where gas is used1 the small lamp known as 8,bunsen's0 is the most convenient and inexpensive4 ,it gives great heat1 is free from smoke1 and is readily affixed to the common gas-burner by a few feet of india-rubber tubing4 ,the light from these lamps is small1 but this is little or no drawback to their use4 ,where gas is not available1 the common spirit-lamps may be used1 which are very clean and answer every purpose4 ,in applying the required heat to the slides1 covers1 c41 it is necessary in many cases to ensure uniformity1 otherwise there is danger of the glass being broken4 ,for this purpose a brass plate at least three inches wide1 somewhat longer1 and one-eighth of an inch thick1 must be procured4 ,it should then be affixed to a stand1 so that it may be readily moved higher or lower1 in order that the distance from the lamp may be changed at will1 and thus the degree of heat more easily regulated4 ,this has also the advantage of enabling the operator to allow his slides1 c41 to cool more gradually1 which1 in some cases1 is absolutely necessary1--as in fusing some of the salts1 c4 ,in order to get rid of air-bubbles1 which are frequently disagreeable enemies to the mounter of objects1 an air-pump is often very useful4 ,this is made by covering a circular plate of metal with a bell-glass1 both of which are ground so finely at the edges that greasing the place of contact renders it air-tight4 ,the pump is then joined to the metal plate underneath1 and worked with a small handle like a common syringe4 ,by turning a small milled head the air may be allowed to re-enter when it is required to remove the bell-glass and examine or perform any operation upon the object4 ,the mode of using this instrument will be described hereafter1 but it may be here stated that substitutes have been devised for this useful apparatus2 but as it is now to be obtained at a low cost1 it is hardly worth while to consider them4 ,much time is1 in many instances1 certainly saved by its use1 as a very long immersion in the liquids would be required to expel the bubbles1 where the air-pump would remove them in an hour4 ,the next thing to be considered is what may be termed ,,cements1 some of which are necessary in every method of mounting objects for the microscope4 ,of these will be given the composition where it is probable the young student can make use of it2 but many of them are so universally kept as to be obtainable almost anywhere2 and when small quantities only are required1 economy suffers more from home manufacture than from paying the maker's profit4 ,amongst these1 ,,canada ,,balsam may1 perhaps1 be termed the most necessary1 as it is generally used for the preservation of many transparent objects4 ,it is a thick liquid resin of a light amber colour1 which on exposure to the atmosphere becomes dry and hard even to brittleness4 ,for this reason it is seldom used as a cement alone where the surface of contact is small1 as it would be apt to be displaced by any sudden shock1 especially when old4 ,in the ordinary method of using1 however1 it serves the double purpose of preserving the object and fixing the thin glass cover2 whilst the comparatively large space upon which it lies lessens the risk of displacement4 ,by keeping1 this substance becomes thicker2 but a very little warmth will render it liquid enough to use even when to some extent this change has taken place4 ,when heated1 however1 for some time and allowed to cool1 it becomes hardened to any degree1 which may be readily regulated by the length of time it has been exposed1 and the amount of heat to which it has been subjected4 ,on account of this property it is often used with chloroform3 the balsam is exposed to heat until1 on cooling1 it assumes a glassy appearance2 it is then dissolved in pure chloroform until it becomes of the consistence of thick varnish4 ,this liquid is very convenient in some cases2 as air-bubbles are much more easily got rid of than when undiluted ,canada balsam is used4 ,it also dries readily1 as the chloroform evaporates very quickly1 for which reason it must be preserved in a closely-stoppered bottle4 ,it has been said that this mixture becomes cloudy with long keeping1 but ,i have not found it so in any cases where ,i have used it4 ,should it1 however1 become so1 a little heat will readily dispel the opacity4 ,the ordinary balsam1 if exposed much to the air whilst being used1 becomes thicker1 as has been already stated4 ,it may be reduced to the required consistency with common turpentine1 but ,i have often found this in some degree injurious to the transparency of the balsam1 and the amalgamation of the two is by no means perfect4 7,see also ,chapter ,,iii47 ,the cheapness of the article renders it no extravagance to use it always undiluted2 and when preserved in a bottle with a hollow cover fitting tightly around the neck1 both surfaces being finely ground1 it remains fit for use much longer than in the ordinary jar4 ,,asphaltum4--,this substance is dissolved in linseed oil1 turpentine1 or naphtha1 and is often termed 8,brunswick black40 ,it is easily worked1 but is not generally deemed a trustworthy cement1 as after a time it is readily loosened from its ground4 ,it is1 however1 very useful for some purposes 7such as 8finishing0 the slides71 as it dries quickly4 ,i shall1 however1 mention a modification of this cement a little further on4 ,,marine ,,glue4--,no cement is more useful or trustworthy for certain purposes than this4 ,it is made in various proportions2 but one really good mixture is--equal parts of india-rubber and gum shellac2 these are dissolved in mineral naphtha with heat4 ,it is1 however1 much better to get it from the opticians or others who keep it4 ,it requires heat in the application1 as will be explained in ,chapter ,,iv42 but it is soluble in few1 if any1 liquids used by the microscopist1 and for that reason is serviceable in the manufacture of cells1 c4 ,where two pieces of glass are to be firmly cemented together1 it is almost always employed2 and in all glass troughs1 plates with ledges1 c41 the beginner may find examples of its use4 ,,gold ,,size4--,this substance may always be procured at any colourman's shop4 ,the process of its preparation is long and tedious4 ,it is1 therefore1 not necessary to describe it here4 ,dr4 ,carpenter says that it is very durable1 and may be used with almost any preservative liquids1 as it is acted upon by very few of them1 turpentine being its only true solvent4 ,if too thin1 it may be exposed for awhile to the open air1 which by evaporation gradually thickens it4 ,care must be taken1 however1 not to render it too thick1 as it will then be useless4 ,a small quantity should be kept on hand1 as it is much more adhesive when old4 ,,liquid ,,glue is another of these cements1 which is made by dissolving gum shellac in naphtha in such quantity that it may be of the required consistency4 ,this cement appears to me almost worthless in ordinary work1 as its adherence can never be relied upon2 but it is so often used and recommended that an enumeration of cements might be deemed incomplete without it4 ,even when employed simply for varnishing the outside of the glass covers1 for appearance' sake alone1 it invariably chips4 ,where1 however1 oil is used as a preservative liquid1 it serves very well to attach the thin glass2 but when this is accomplished1 another varnish less liable to 8chip0 must always be laid upon it4 7,see ,chapter ,,iv47 ,,black ,,japan4--,this is prepared from oil of turpentine1 linseed oil1 amber1 gum anime1 and asphalt4 ,it is troublesome to make1 and therefore it is much better to procure it at the shops4 ,it is a really good cement1 and serves very well to make shallow cells for liquids1 as will be described in ,chapter ,,iv4 ,the finished cell should be exposed for a short time to the heat of what is usually termed a 8cool oven40 ,this renders it very durable1 and many very careful manipulators make use of it for their preparations4 ,,electrical ,,cement4--,this will be found very good for some purposes hereinafter described4 ,to make it1 melt together-- #e parts of resin4 #a 0 beeswax4 #a 0 red ochre4,a ,a ,dr4 ,griffiths says that the addition of #b parts of ,canada balsam renders this cement much more adhesive to the glass4 ,it must be used whilst hot1 and as long as it retains even slight warmth can be readily moulded into any form4 ,it is often employed in making shallow cells for liquids1 as before mentioned4 ,,gum-,,water is an article which nobody should ever be without2 but labels1 or indeed any substance1 affixed to glass with common gum1 are so liable to leave it spontaneously1 especially when kept very dry1 that ,i have lately added five or six drops of glycerine to an ounce of the gum solution4 ,this addition has rendered it very trustworthy even on glass1 and now ,i never use it without4 ,this solution cannot be kept long without undergoing fermentation1 to prevent which the addition of a small quantity of any essential oil 7as oil of cloves1 c471 or one-fourth of its volume of alcohol1 may be made1 which will not interfere in any way with its use4 ,there is what is sometimes termed an extra adhesive gum-water1 which is made with the addition of isinglass1 thus3--,dissolve two drachms of isinglass in four ounces of distilled vinegar2 add as much gum arabic as will give it the required consistency4 ,this will keep very well1 but is apt to become thinner1 when a little more gum may be added4 ,all these1 except one or two1 are liquid1 and must be kept in stoppered bottles1 or1 at least1 as free from the action of the air as possible4 ,when any two substances are to be united firmly1 ,i have termed the medium employed 8a cement20 but often the appearance of the slides is thought to be improved by drawing a coloured ring upon them1 extending partly on the cover and partly on the slide1 hiding the junction of the two4 ,the medium used in these cases ,i term ,a ,,varnish1 and hereinafter mention one or two4 ,of course1 the tenacity is not required to be so perfect as in the cements4 ,,sealing-,,wax ,,varnish is prepared by coarsely powdering sealing wax1 and adding spirits of wine2 it is then digested at a gentle heat to the required thickness4 ,this is very frequently used to 8finish0 the slides1 as before mentioned1 and can easily be made of any colour by employing different kinds of sealing-wax2 but is very liable to 8chip0 and leave the glass4 ,,black ,,varnish is readily prepared by adding a small quantity of lamp-black to gold-size and mixing intimately4 ,dr4 ,carpenter recommends this as a good finishing varnish1 drying quickly and being free from that brittleness which renders some of the others almost worthless2 but it should not be used in the first process when mounting objects in fluid4 ,amongst these different cements and varnishes ,i worked a long time without coming to any decision as to their comparative qualities1 though making innumerable experiments4 ,the harder kinds were continually cracking1 and the softer possessed but little adhesive power4 ,to find hardness and adhesiveness united was my object1 and the following possesses these qualities in a great degree3-- ,india-rubber drachm4 ,asphaltum #d oz4 ,mineral naphtha #aj 0 ,dissolve the india-rubber in the naphtha1 then add the asphaltum--if necessary heat must be employed4 ,this is often used by photographers as a black varnish for glass1 and never cracks1 whilst it is very adhesive4 ,dr4 ,carpenter1 however1 states that his experience has not been favourable to it2 but ,i have used it in great quantities and have never found it to leave the glass in a single instance when used in the above proportions4 ,the objections to it are1 however1 ,i think easily explained1 when it is known that there are many kinds of pitch1 c41 from coal1 sold by the name of asphaltum1 some of which are worthless in making a microscopic cement4 ,when used for this purpose1 the asphaltum must be genuine and of the best quality that can be bought4 ,the above mixture serves a double purpose--to unite the cell to the slide1 and also as a 8finishing0 varnish4 ,but it is perhaps more convenient to have two bottles of this cement1 one of which is thicker than common varnish1 to use for uniting the cell1 c42 the other liquid enough to flow readily1 which may be employed as a surface varnish in finishing the slides4 ,the brushes or camel-hair pencils should always be cleaned after use2 but with the asphalt varnish above mentioned it is sufficient to wipe off as carefully as possible the superfluous quantity which adheres to the pencil1 as1 when again made use of1 the varnish will readily soften it2 but1 of course1 it will be necessary to keep separate brushes for certain purposes4 ,here it may be observed that every object should be labelled with name and any other descriptive item as soon as mounted4 ,there are many little differences in the methods of doing this4 ,some write with a diamond upon the slide itself2 but this has the disadvantage of being not so easily seen4 ,for this reason a small piece of paper is usually affixed to one end of the slide1 on which is written what is required4 ,these labels may be bought of different colours and designs2 but the most simple are quite as good1 and very readily procured4 ,take a sheet of thin writing paper and brush over one side a strong solution of gum1 with the addition of a few drops of glycerine as above recommended2 allow this to dry1 and then with a common gun-punch stamp out the circles1 which may be affixed to the slides by simply damping the gummed surface1 taking care to write the required name1 c41 upon it before damping it1 or else allowing it to become perfectly dry first4 ,there is one difficulty which a beginner often experiences in sorting and mounting certain specimens under the microscope1 viz41 the inversion of the objects2 and it is often stated to be almost impossible to work without an erector4 ,but this difficulty soon vanishes1 the young student becoming used to working what at first seems in contradiction to his sight4 ,let it be understood1 that in giving the description of those articles which are usually esteemed necessary in the various parts of microscopic manipulation1 ,i do not mean to say that without many of these no work of any value can be done4 ,there are1 as all will allow1 certain forms of apparatus which aid the operator considerably2 but the cost may be too great for him4 ,a little thought1 however1 will frequently overcome this difficulty1 by enabling him to make1 or get made1 for himself1 at a comparatively light expense1 something which will accomplish all he desires4 ,as an example of this1 a friend of mine made what he terms his 8universal stand10 to carry various condensers1 c41 c41 in the following way3--,take a steel or brass wire1 three-sixteenths or one-quarter inch thick and six or eight inches long2 8tap0 into a solid1 or make rough and fasten with melted lead into a hollow1 ball4 7,the foot of a cabinet or work-box answers the purpose very well47 ,in the centre of a round piece of tough board1 three inches in diameter1 make a hemispherical cavity to fit half of the ball1 and bore a hole through from the middle of this cavity1 to allow the wire to pass4 ,take another piece of board1 about four inches in diameter1 either round or square1 and one-and-a-half or two inches thick1 make a similar cavity in its centre to receive the other half of the ball1 but only so deep as to allow the ball to fit tightly when the two pieces of board are screwed together1 which last operation must be done with three or four screws4 ,let the hole for the wire in the upper part be made conical 7base upwards71 and so large as only to prevent the ball from escaping from its socket1 in order that the shaft may move about as freely as possible4 ,turn a cavity1 or make holes1 in the bottom of the under piece1 and fill with lead to give weight and steadiness4 ,this1 painted green bronze and varnished1 looks neat2 and by having pieces of gutta-percha tubing to fit the shaft1 a great variety of apparatus may be attached to it4 ,again1 a 8condenser0 is often required for the illumination of opaque objects4 ,my ingenious friend uses an 8engraver's bottle0 7price #f;d471 fills it with water1 and suspends it betwixt the light and the object4 ,where the light is very yellow1 he tints the water with indigo1 and so removes the objectionable colour4 ,i merely mention these as examples of what may be done by a little thoughtful contrivance1 and to remove the idea that nothing is of much value save that which is the work of professional workmen1 and consequently expensive4 ,,chapter ,,ii4 ,,to ,,prepare ,,and ,,mount ,,objects 8,,dry40 ,the term 8dry0 is used when the object to be mounted is not immersed in any liquid or medium1 but preserved in its natural state1 unless it requires cleaning and drying4 ,i have before stated that thorough cleanliness is necessary in the mounting of all microscopic objects4 ,i may here add that almost every kind of substance used by the microscopist suffers from careless handling4 ,many leaves with fine hairs are robbed of half their beauty1 or the hairs1 perhaps1 forced into totally different shapes and groups2 many insects lose their scales1 which constitute their chief value to the microscopist2 even the glass itself distinctly shows the marks of the fingers if left uncleaned4 ,every object must also be thoroughly dry1 otherwise dampness will arise and become condensed in small drops upon the inner surface of the thin glass cover4 ,this defect is frequently met with in slides which have been mounted quickly2 the objects not being thoroughly dry when enclosed in the cell4 ,many of the cheap slides are thus rendered worthless4 ,even with every care it is not possible to get rid of this annoyance occasionally4 ,for the purpose of mounting opaque objects 8dry10 discs were at one time very commonly made use of4 ,these are circular pieces of cork1 leather1 or other soft substance1 from one-quarter to half inch in diameter1 blackened with varnish or covered with black paper1 on which the object is fixed by gum or some other adhesive substance4 ,they are usually pierced longitudinally by a strong pin1 which serves for the forceps to lay hold of when being placed under the microscope for examination4 ,sometimes objects are affixed to both sides of the disc1 which is readily turned when under the object-glass4 ,the advantage of this method of mounting is the ease with which the disc may be moved1 and so present every part of the object to the eye save that by which it is fastened to the disc4 ,on this account it is often made use of when some particular subject is undergoing investigation1 as a number of specimens may be placed upon the discs with very little labour1 displaying all the parts4 ,but where exposure to the atmosphere or small particles of dust will injure an object1 no advantage which the discs may possess should be considered1 and an ordinary covered cell should be employed4 ,small pill-boxes have been used1 to the bottom of which a piece of cork has been glued to afford a ground for the pin or other mode of attachment2 but this is liable to some of the same faults as the disc1 and it would be unwise to use these for permanent objects4 ,messrs4 ,smith and ,beck have lately invented1 and are now making1 a beautiful small apparatus1 by means of which the disc supporting the object can be worked with little or no trouble into any position that may prove most convenient1 whilst a perforated cylinder serves for the reception of the discs when out of use1 and fits into a case to protect them from dust4 ,a pair of forceps is made for the express purpose of removing them from the case and placing them in the holder4 ,all dry objects1 however1 which are to be preserved should be mounted on glass slides in one of the cells 7described in ,chapter ,i47 best suited to them4 ,where the object is to be free from pressure1 care must be taken that the cell is deep enough to ensure this4 ,when the depth required is but small1 it is often sufficient to omit the card1 leather1 or other circles1 and with the 8turn-table0 before described1 by means of a thick varnish and camel-hair pencil1 to form a ring of the desired depth2 but should the varnish not be of sufficient substance to give such 8walls0 at once1 the first application may be allowed to dry1 and a second made upon it4 ,a number of these may be prepared at the same time1 and laid by for use4 ,when liquids are used 7see ,chapter ,,iv471 ,dr4 ,carpenter recommends gold-size as a good varnish for the purpose1 and this may be used in 8dry0 mountings also4 ,i have used the asphaltum and india-rubber 7mentioned in ,chapter ,i471 and found it to be everything ,i could wish4 ,the cells1 however1 must be thoroughly dry1 and when they will bear the heat they should be baked for an hour at least in a tolerably cool oven1 by which treatment the latter becomes a first-rate medium4 ,all dry objects which will not bear pressure must be firmly fastened to the slide1 otherwise the necessary movements very often injure them1 by destroying the fine hairs1 c4 ,for this purpose thin varnishes are often used1 and will serve well enough for large objects1 but many smaller ones are lost by adopting this plan1 as for a time1 which may be deemed long enough to harden the varnish1 they exhibit no defect1 but in a while a 8wall0 of the plastic gum gathers around them1 which refracts the light1 and thus leads the student to false conclusions4 ,in all finer work1 where it is necessary to use any method of fixing them to the slide1 a solution of common gum1 with the addition of a few drops of glycerine 7,chapter ,i471 will be found to serve the purpose perfectly4 ,it must1 however1 be carefully filtered through blotting paper1 otherwise the minute particles in the solution interfere with the object1 giving the slide a dusty appearance when under the microscope4 ,when mounting an object in any of these cells1 the glass must be thoroughly cleaned1 which may be done with a cambric handkerchief1 after the washing mentioned in ,chapter ,i4 ,if the object be large1 the point of a fine camel-hair pencil should be dipped into the gum solution1 and a minute quantity of the liquid deposited in the cell where the object is to be placed1 but not to cover a greater surface than the object will totally hide from sight4 ,this drop of gum must be allowed to dry1 which will take a few minutes4 ,breathe then upon it two or three times1 holding the slide not far from the mouth1 which will render the surface adhesive4 ,then draw a camel-hair pencil through the lips1 so as to moisten it slightly 7when anything small will adhere to it quite firmly enough71 touch the object and place it upon the gum in the desired position4 ,this must be done immediately to ensure perfect stability1 otherwise the gum will become at least partially dry and only retain the object imperfectly4 ,when1 however1 the objects are so minute that it would be impossible to deposit atoms of gum small enough for each one to cover1 a different method of proceeding must be adopted4 ,in this case a small portion of the same gum solution should be placed upon the slide1 and by means of any small instrument--a long needle will serve the purpose very well--spread over the surface which will be required4 ,the quantity thus extended will be very small1 but by breathing upon it may be prevented drying whilst being dispersed4 ,this1 like the forementioned1 should be then allowed to dry2 and whilst the objects are being placed on the prepared surface1 breathing upon it as before will restore the power of adherence4 ,when gum or other liquid cement has been used to fix the objects to the glass1 the thin covers must not be applied until the slide has been thoroughly dried1 and all fear of dampness arising from the use of the solution done away with4 ,warmth may be safely applied for the purpose1 as objects fastened by this method are seldom1 if ever1 found to be loosened by it4 ,as objects are met with of every thickness1 the cells will be required of different depths4 ,there is no difficulty in accommodating ourselves in this--the deeper cells may be readily cut out of thick leather1 card1 or other substance preferred 7as mentioned in ,chapter ,i474 ,cardboard is easily procured of almost any thickness2 but sometimes it is convenient to find a thinner substance even than this4 ,when thin glass is laid upon a drop of any liquid upon a slide1 every one must have observed how readily the liquid spreads betwixt the two3 just so when any thin varnish is used to surround an object of little substance1 excessive care is needed lest the varnish should extend betwixt the cover and slide1 and so render it worthless4 ,the slightest wall1 however1 prevents this from taking place1 so that a ring of common paper may be used1 and serve a double purpose where the objects require no deeper cell than this forms4 ,many objects1 however1 are of such tenuity--as the leaves of many mosses1 some of the ,diatomace1 scales of insects1 c4--that no cell is requisite excepting that which is necessarily formed by the medium used to attach the thin glass cover to the slide2 and where the slide is covered by the ornamental papers mentioned in ,chapter ,i41 and pressure does not injure the object1 even this is omitted1 the thin glass being kept in position by the cover2 but slides mounted in this manner are frequently injured by dampness1 which soon condenses upon the inner surfaces and interferes both with the object and the clearness of its appearance4 ,the thin glass1 then1 is to be united to the slide1 so as to form a perfect protection from dust1 dampness1 or other injurious matter1 and yet allow a thoroughly distinct view of the object4 ,this is to be done by applying to the glass slide round the object some adhesive substance1 and with the forceps placing the thin glass cover 7quite dry and clean7 upon it4 ,a gentle pressure round the edge will then ensure a perfect adhesion1 and with ordinary care there will be little or no danger of breakage4 ,for this purpose gold-size is frequently used4 ,the asphalt and india-rubber varnish also will be found both durable and serviceable4 ,whatever cement may be used1 it is well to allow it to become in some measure 8fixed0 and dried2 but where no cell or 8wall0 is upon the slide1 this is quite necessary1 otherwise the varnish will be almost certain to extend1 as before mentioned1 and ruin the object4 ,it may be stated here that gold-size differs greatly in its drying powers1 according to its age1 mode of preparation1 c4 7,chapter ,,iv47 ,should any object be enclosed which requires to be kept flat during the drying of the cement1 it will be necessary to use some of the contrivances mentioned in ,chapter ,i4 ,when the slide is thus far advanced1 there remains the 8finishing0 only4 ,should the student1 however1 have no time to complete his work at once1 he may safely leave it at this stage until he has a number of slides which he may finish at the same time4 ,there are different methods of doing this1 some of which may be here described4 ,if ornamental papers are preferred1 a small circle must be cut out from the centre a little less than the thin glass which covers the object4 ,another piece of coloured paper is made of the same size1 and a similar circle taken from its centre also1 or both may be cut at the same time4 ,the slide is then covered round the edges with paper of any plain colour1 so that it may extend about one-eighth of an inch over the glass on every side4 ,the ornamental paper is then pasted on the 8object0 surface of the glass1 so that the circle shows the object as nearly in the centre as possible1 and covers the edges of the thin glass4 ,the other coloured paper is then affixed underneath with the circle coinciding with that above4 ,and here ,i may observe1 that when this method is used there is no necessity for the edges of the slide to be 8ground10 as all danger of scratching1 c41 is done away with by the paper cover4 ,many now use paper covers1 about one and a half inches long1 on the upper side of the slide only1 with the centre cut out as before1 with no other purpose than that of hiding the edge of the thin glass where it is united to the slide4 ,the method of 8finishing10 however1 which is mostly used at the present time1 is to lay a coating of varnish upon the edge of the thin glass1 and extend it some little way on the slide4 ,when a black circle is required1 nothing serves the purpose better than the gold-size and lamp-black1 or the asphalt and india-rubber varnish1 neither of which is liable to chip2 but when used for this1 the latter should be rather thinner1 as before advised4 ,some of these varnishes are preferred of different colours1 which may be made by using the different kinds of sealing-wax1 as described in ,chapter ,i42 but they are always liable to the defects there mentioned4 ,this circle cannot be made in any other way but by one of those contrivances which have now centred in ,shadbolt's turntable4 ,a very little practice will enable the young student to place his slide so that the circle may be uniform with the edge of the thin glass4 ,the slide is now complete1 except the addition of the name and any other particulars which may be desirable4 ,for this purpose one of the methods described in ,chapter ,i4 must be employed4 ,amongst the various classes of microscopic objects now receiving general attention1 the ,diatomace may be placed in a prominent position4 ,they afford endless opportunities of research1 and some very elaborate works have already been issued concerning them4 ,professor ,smith's may be mentioned as one containing1 perhaps1 the best illustrations4 ,the young student may wish to know what a diatom is4 ,the 8,micrographic ,dictionary0 gives the following definition3--8,a family of confervoid ,alg1 of very peculiar character1 consisting of microscopic brittle organisms40 ,they are now looked upon by almost all of our scientific men as belonging to the vegetable kingdom1 though some few still assign them to the animal4 ,they are almost invariably exceedingly small1 so that the unaided eye can perceive nothing on a prepared slide of these organisms but minute dust4 ,each separate portion1 which is usually seen when mounted1 is termed a 8frustule10 or 8testule30 this consists of two similar parts1 composed of silica1 between and sometimes around which is a mass of viscid matter called the 8endochrome40 ,they are found in almost every description of water1 according to the variety3 some prefer sea-water1 others fresh1 and many are seen nowhere but in that which is a mixture of both1 as the mouths of rivers1 c4 ,ditches1 ponds1 cisterns1 and indeed almost every reservoir1 yield abundance of these forms4 ,they are not1 however1 confined to 8present0 life2 but1 owing to the almost indestructible nature of their siliceous covering1 they are found in a fossil state in certain earths in great abundance1 and are often termed 8fossil ,infusoria40 ,upon these frustules are generally to be seen lines1 or 8markings10 of different degrees of minuteness1 the delicacy of which often serves the purpose of testing the defining power of the object-glasses4 ,some of the frustules are triangular1 others circular1 and1 indeed1 of almost every conceivable shape1 many of them presenting us with exquisitely beautiful designs4 ,the markings1 however1 are seldom seen well1 if at all1 until the frustules are properly prepared1 the different methods of accomplishing which will be given a little further on4 ,the collection of the fresh diatoms is so closely connected with their preservation1 that a few notes may be given upon it before we pass on4 ,for this purpose a number of small bottles must be provided1 which may be placed in a tin box1 with a separate apartment for each1 so that all chance of breakage may be done away with4 ,the diatoms are generally of a light brown colour2 and where they are observed in the water1 the bottle may be so placed1 with the mouth closed by the finger1 that when the finger is withdrawn the water will rush in1 carrying the diatoms also4 ,if they are seen upon plants1 stones1 or any other substance1 they may generally be detached and placed in the bottle4 ,when there is a green covering upon the surface of the water1 a great quantity of diatoms is usually found amongst it2 as also upon the surface of the mud in those ponds where they abound4 ,in these cases1 a broad flat spoon will be found very useful1 and one is now made with a covering upon the broader portion of it to protect the enclosed matter from being so readily carried off whilst bringing it to the surface again4 ,where there is any depth of water1 and the spoon will not reach the surface of the mud1 the bottle must be united to a long rod1 and being then carried through the upper portion with the mouth downwards1 no water will be received into it2 but on reaching the spot required1 the bottle-mouth may be turned up1 and thus become filled with what is nearest4 ,from the stomachs of common fish--as the cod1 sole1 haddock1 c4--many specimens of ,diatomace may be obtained1 but especially from the crab1 oyster1 mussel1 and other shell-fish4 ,professor ,smith states that from these curious receptacles he has taken some with which he has not elsewhere met4 ,to remove them from any of the small shell-fish1 it is necessary to take the fish or stomach from the shell1 and immerse it in strong hot acid 7nitric is the best7 until the animal matter is dissolved1 when the residue must be washed and treated as the ordinary ,diatomace hereinafter described4 ,many diatoms are seen best when mounted in a dry state1 the minute markings becoming much more indistinct if immersed in liquid or balsam2 and for this reason those which are used as test objects are usually mounted dry4 ,many kinds also are now prepared in this way1 as opaque objects to be examined with the lieberkuhn1 and are exquisitely beautiful4 ,others1 however1 are almost invariably mounted in balsam2 but as these will be again referred to in ,chapter ,,iii41 and require the same treatment to fit them for the slide1 it will not be out of place to describe the cleaning and preparation of them here4 ,as before stated1 there is much matter surrounding them which must be got rid of before the 8siliceous covering0 can be shown perfectly4 ,as1 however1 we may first wish to become acquainted in some degree with what we have to do1 it is well to take a small piece of talc1 and place a few of the diatoms upon it4 ,this may be held over the flame of the spirit-lamp until all the surrounding matter is burnt away1 and a tolerable idea may be thus obtained as to the quality of our treasure4 ,in some cases it is well to use this burning operation alone in mounting specimens of diatoms1 when they may be placed in their natural state upon the thin glass1 burnt for awhile upon the platinum plate1 hereafter described1 and mounted dry or in balsam4 ,in the preparation and cleaning of ,diatomace1 there is little satisfaction unless these operations have been successfully performed1 as a very small portion of foreign matter seriously interferes with the object4 ,the mode of preparing them varies even amongst the most experienced4 ,it will be found1 therefore1 most satisfactory to examine the principal of these separately1 although it may be at the risk of some little repetition4 ,the method which is the most frequently made use of is the following3--,place the 8gathering0 containing the ,diatomace in a small glass or porcelain vessel1 add strong nitric acid1 and1 by the aid of ,bunsen's burner or spirit-lamp1 boil for some minutes4 ,from time to time a drop of the mixture may be put upon a slide1 and examined under the microscope to see if all foreign matter be got rid of4 ,when the valves are clean1 the vessel containing them must be filled with water1 and the whole left for an hour or two1 so that all the diatoms may settle perfectly4 ,the liquid must then be poured off carefully1 or drained away by the aid of a syphon1 so that none of the diatoms are removed with it4 ,indeed1 it is well to examine the liquid drained off each time with the microscope1 as the finer forms are frequently lost in the washings4 ,the vessel must then be refilled with pure water1 allowed to settle1 and drained as before4 ,this washing must be repeated until a drop being placed upon a slide and evaporated leaves no crystals4 ,when it is desirable to preserve the diatoms in this state before mounting 7which process will be described in another place71 they may be placed in a small phial with a little distilled water4 ,there are many cases in which the above method will not effect a perfect cleansing1 as certain substances with which the diatoms are frequently mixed are not soluble in nitric acid4 ,for this reason the following method is resorted to3--,take a quantity of the matter containing the ,diatomace and wash first with pure water1 to get rid of all the impurities possible4 ,allow this to settle perfectly and decant the water4 ,add hydrochloric acid gradually1 and when all effervescence has subsided1 boil for some minutes by aid of the lamp4 ,when cool and the particles have subsided1 decant the hydrochloric and add nitric acid4 ,the boiling must then be repeated until a drop of the liquid when placed under the microscope shows the valves or 8frustules0 clean4 ,after allowing the diatoms to settle1 the acid must be decanted1 and pure water substituted4 ,the washing must be repeated as in the former process until all the remains of crystals or acid are removed1 when the specimens may be preserved in small phials as stated above4 ,such are the usual modes of treating the ,diatomace1 but there are certain cases in which particular methods are required to give anything like perfect results4 ,persons of great experience combine a variety of treatments1 and thus obtain better and more uniform specimens4 ,perhaps it will be advantageous to give the young student the process adopted by one of the most successful preparers of these objects2 but ,i will first state the different methods of mounting the cleaned diatoms dry3 how to employ ,canada balsam and fluid in their preservation will be elsewhere described4 ,it was before stated that the diatoms when cleansed might be preserved in small phials of distilled water4 ,when required for mounting1 shake the phial1 and with a thin glass tube or rod take up a drop of the fluid and spread it upon the surface of the slide in the desired position4 ,this must then be allowed to dry gradually1 or by the aid of the lamp if necessary1 without being shaken or interfered with1 otherwise uniformity of dispersion will be prevented4 ,when thoroughly dry1 a thin ring of one of the adhesive varnishes--gold-size will be found as good as any--may be drawn round the diatoms1 and allowed to dry in a slight degree4 ,the slide and thin glass cover should then be warmed and the latter gently pressed upon the ring of varnish until the adhesion all round is complete4 ,as some of the diatoms require object-glasses of extremely high power1 and1 consequently1 short focus1 to show them1 they must be as close to the outer surface of the cover as possible4 ,for this reason they are sometimes placed upon the under side of the thin glass1 as follows4 ,clean the surfaces of the slide and cover1 and with the rod or pipe place the liquid containing the diatoms upon the thin glass1 and dry as before4 ,trace the ring to receive the cover upon the slide1 and when almost dry1 warm both and proceed as above4 ,whichever of these methods is employed1 the outer ring of coloured varnish may be applied as elsewhere described and the slide finished4 ,the diatoms are also sometimes mounted betwixt two thin glasses1 as described in ,chapter ,i41 so that the light by which they are examined may receive as little interference as possible1 and that an achromatic condenser may be brought into focus under the slide4 ,of the various modes of cleaning and mounting the ,diatomace1 ,i believe that the following may be safely recommended as affording results of the very best quality4 ,my friend1 ,mr4 ,t4 ,g4 ,rylands1 gave it to me as that which he prefers1 and ,i can safely say that his numerous slides are at least equal to any ,i have ever seen4 ,i will give it just as ,i received it from him1 though there may be some little repetition of what has been said elsewhere1 as he does not appropriate any part of it as his own4 ,he says3--,in this branch of mounting1 general rules alone can be laid down1 because the gatherings may contain iron1 lime1 fine silt1 or vegetable matter under conditions for special treatment1 and consequently the first step should be to experiment on various kinds4 ,in gathering diatoms much labour is saved by judgment and care2 hence it is desirable to get acquainted with them in their growing condition1 so that when recognised upon the sands or other spots they may be carefully removed by the aid of the spoon or small tin scoop before described4 ,when growing upon alg or other plants1 the plants and diatoms together may be carried home1 in which case they must be simply drained and not washed or pressed1 in order that the diatoms be not lost4 ,as it is always desirable to examine the gathering on the ground1 a 8,gairdner's hand microscope0 with powers from #hj to #bjj diameters will be found very useful4 ,the best gatherings are those which represent one species abundantly4 ,those which are mixed may be rejected1 unless they are seen to contain something valuable or important1 as the object should be not so much to supply microscopical curiosities as to collect material which is available for the study of nature4 ,the gathering when carried home should always be carefully examined before anything is done with it2 not only on account of the additional information thus acquired1 but also because it often happens that a specimen should be mounted in fluid 7see ,chapter ,,iv47 in the condition in which it is gathered1 as well as cleaned and mounted in balsam 7,chapter ,,iii47 and dry4 ,where the gathering is taken from sand1 the whole may be shaken up in water as a preliminary operation1 when much of the sand will be separated by its own weight4 ,the lime test1 however1 should be applied1 viz4--a small portion of hydrochloric acid1 and if there be effervescence it must be dissolved out by this means4 ,from ,alg and other weeds diatoms may be detached by agitating the whole together in a weak solution of nitric acid--about one of pure acid to twenty or thirty of water1 as it must be sufficiently weak to free the diatoms without destroying the matter to which they adhere4 ,the diatoms may then be separated by sifting through coarse muslin1 which will retain the ,alg1 c4 ,the process of cleaning will vary according to circumstances4 ,some gatherings require to be boiled only a few minutes in nitric acid2 but the more general plan where they are mixed with organic or other foreign matter1 is to boil them in pure sulphuric acid until they cease to grow darker in colour 7usually from a half to one minute71 and then to add1 drop by drop to avoid explosions1 a cold saturated solution of chlorate of potash until the colour is discharged1 or1 in case the colour does not disappear1 the quantity of the solution used is at least equal to that of the acid4 ,this operation is best performed in a wide-mouthed ordinary beaker glass1,b a test-tube being too narrow4 ,the mixture whilst boiling should be poured into thirty times its bulk of cold water1 and the whole allowed to subside4 ,the fluid must then be carefully decanted and the vessel re-supplied once or twice with pure water1 so as to get rid of all the acid4 ,the gathering may then be transferred to a small boiling glass or test-tube1 and--the water being carefully decanted--boiled in the smallest available quantity of nitric acid1 and washed as before4 ,this last process has been found necessary from the frequent appearance of minute crystals1 which cannot otherwise be readily disposed of without the loss of a considerable proportion of diatoms4 ,b ,these glasses are round1 about six inches high1 and usually contain about eight ounces4 ,they are rather wider at the bottom1 tapering gradually to the top1 and may be generally procured at the chemists1 c4 ,i may here mention that the washing glasses used by ,mr4 ,rylands are stoppered conical bottles varying in capacity from two ounces to one quart2 the conical form being employed to prevent the adherence of anything to the side2 they are 8stoppered0 to render them available in the shaking process about to be described4 ,the gathering1 freed from acid1 is now put into two inches depth of water1 shaken vigorously for a minute or two1 and allowed to subside for half an hour1 after which the turbid fluid must be carefully decanted4 ,this operation must be repeated until all the matter is removed which will not settle in half an hour4 ,the fluid removed should be examined by a drop being put upon a slide1 as in some cases very light diatoms have been found to come off almost pure in one or more of these earlier washings4 ,the quantity of water and time of subsidence given may be taken generally1 but may require to be modified according to circumstances and the judgment of the operator4 ,by the repetition and variation of this process--the shaking being the most important part--the gathering1 if a pure one1 will be sufficiently clean4 ,if1 however1 it contains a variety of species and forms1 it may require to be divided into different densities4 ,in some cases1 however1 it is best to divide the gathering as a preliminary operation1 which may be done by agitating it in a quantity of water and decanting what does not readily subside4 ,the heavier and the lighter portions are then to be treated as two separate boilings4 ,but when the cleansing has been carried to the above stage and this division is required1 the plan must be somewhat as follows3--,the gathering must be shaken in a test-tube with six inches of water1 and then allowed to subside until one inch at the top remains pure4 ,about three inches are then to be carefully withdrawn by a pipette1 when the tube may be filled up and the operation repeated4 ,the three lower inches also may then be decanted and examined4 ,the gathering is thus divided into three portions1 viz4--that which was withdrawn by the pipette1 that which remained floating in the lower three inches of water in the tube1 and that which had settled at the bottom4 ,an examination of these will inform the operator how to obtain that particular density of gathering which he desires1 and how far it is worth while to refine this process of elutriation2 for in cases of necessity any one1 or all three1 of these densities may be operated upon in the same way to separate a particular diatom4 ,as occasional aids1 it may be remarked1 that in some cases liquor ammoni may be used in place of water1 as it often separates fine dirt1 which is not otherwise easily got rid of4 ,some fossil deposits require to be treated with a boiling solution of carbonate of soda to disintegrate them2 but this operation requires great care1 lest the alkali should destroy the diatoms4 ,vegetable silicates also sometimes require to be removed by a solution of carbonate of soda2 but as the frustules of the diatoms themselves are but vegetable silica1 even more care is required in this case4 ,it may be well to mention1 that some diatoms are so imperfectly siliceous that they will not bear boiling in acid at all4 ,some of these may be allowed to stand in cold nitric acid some time1 whilst others of a smaller and more delicate character should1 when possible1 be treated with distilled water alone4 ,we will now consider the mode of mounting the prepared diatoms1 which1 if used dry 7as described in this chapter71 should be carefully washed two or three times with the purest distilled water4 ,in this branch1 as in every other1 each collector gives preference to that method in which he is an adept4 ,thus the diatoms may be placed on the under side of the cover1 to be as near to the object-glass as possible1 or upon the slide itself2 and each plan has its advocates4 ,whichsoever of these is used1 nothing seems more simple to the novice than a tolerably equal dispersion of the objects upon the slide or cover2 but this is by no means so readily accomplished1 consequently ,i give ,mr4 ,rylands' method1 as his slides are perfect in this respect also4 ,he always places the diatoms upon the thin glass cover4 ,it is not sufficient1 as is frequently thought1 to take a drop of liquid containing the cleansed material and spread it upon the cover or slide1 as without some additional precaution that uniform and regular distribution of the specimens is not obtained which is desirable4 ,in order to effect this1 let a drop of the cleansed gathering be diluted sufficiently for the purpose--how much must be determined in each case by experiment--and let the covers to be mounted be cleaned and laid upon the brass plate4 7,see ,chapter ,i47 ,by means of a glass tube1 about one-twelfth of an inch in diameter1 stopped by the wetted finger at the upper end1 take up as much of the diluted material as will form a moderately convex drop extending over the whole cover4 ,when all the covers required are thus prepared1 apply a lamp below the brass plate1 and raise the temperature to a point just short of boiling4 ,by this means the covers will be dried in a few minutes1 and the specimens equally distributed over the whole area4 ,the spread of the fluid upon the covers is facilitated by breathing upon them2 and1 to insure uniformity1 care must be taken to avoid shaking them whilst drying4 ,the best plan is to mount at least half a dozen at once4 ,before mounting1 ,mr4 ,rylands always burns the diatoms upon the glass at a dull red heat1 whether they are used with balsam or dry4 ,this burning1 he says1 is not only an additional cleaning process1 but it effectually fixes the diatoms1 and prevents them floating out if mounted with balsam4 ,the thinnest covers may be burnt without damage if they are placed upon a small piece of platinum foil of the size required1 which should be about one-hundredth of an inch thick1 perfectly flat1 and having three of its edges slightly bent over1 so as to prevent its warping with the heat4 ,the small flame of a spirit-lamp1 or1 where there is gas1 a ,bunsen's burner1 may be employed4 ,the cover should be shaded from direct daylight1 that the action of the flame may be observed more perfectly4 ,care must then be taken to raise the temperature only to the dull red heat before mentioned4 ,the cover will then be in a fit state for mounting as required4 ,it has been stated in another place that it is assumed the operator is not mounting diatoms simply as microscopic objects1 but as instructive specimens4 ,it is not1 therefore1 sufficient to take a single slide as all that is required1 but to have the same diatom prepared in as many ways as possible4 ,the following are the principal3-- #a4 ,mounted crude in fluid 7see ,chapter ,,iv474 #b4 ,burnt crude upon the cover1 and mounted dry or in balsam 7as before mentioned74 #c4 ,mounted dry or in balsam 7see ,chapter ,,iii471 after the cleansing process already described4 ,i will here give ,mr4 ,rylands' method of mounting them dry1 the fluid and balsam preparations being noticed in their respective chapters4 ,the slide with the ring of asphalt1 or black varnish1 should have been prepared some weeks previously1 in order to allow it to dry thoroughly4 ,when required1 it must be held over the spirit-lamp or ,bunsen's burner until the ring of varnish is softened4 ,the burnt cover1 having been heated at the same time1 must then be taken in the forceps and pressed upon the softened varnish until it adheres all round4 ,when cold1 an outer ring of asphalt completes the slide4 ,such is the method which my friend ,mr4 ,t4 ,g4 ,rylands employs in the preparation of diatoms for the microscope4 ,i have said enough concerning his results4 ,it is to be feared1 however1 that to some these several modes of operation may appear lengthy and complicated2 but if read carefully1 and the experiments tried1 they will be found simple enough in practice1 and to occupy much less time than an intelligible description would lead the novice to believe necessary4 ,one of the most fertile as well as the most curious magazines of ,diatomace is guano4 ,the siliceous forms contained therein have been devoured by sea-birds and passed through the stomach uninjured1 and after lying for ages may be cleaned and classified4 ,many of these are not elsewhere met with1 so that the student who is desirous to enter into the study of ,diatomace must be instructed as to the best mode of obtaining them from this source4 ,the particulars to be observed so closely resemble those before mentioned in the treatment of the ordinary diatoms1 that it will be sufficiently explicit to give the outlines of the process4 ,the guano must be first washed in pure water1 allowed to subside perfectly1 and the liquid then poured off4 ,this must be repeated until the top fluid is clear1 and care taken not to decant the liquid until perfect subsidence has taken place4 ,the deposit must then be treated with hydrochloric acid with a gentle heat for an hour or two1 adding a little fresh acid at intervals as long as it excites any effervescence ,after this nitric acid must be substituted for the hydrochloric1 and the heat kept up to almost boiling-point for another hour at least1 adding a little fresh acid as before4 ,when this ceases to act1 the deposit must be allowed to settle perfectly and the acid poured off4 ,all traces of the acid must now be washed away with pure water1 when the remains will be ,diatomace1 the sand contained in the guano1 and a few other forms4 ,some of these may be mounted dry1 as before mentioned1 but the greater portion should be put up in ,canada balsam as described in ,chapter ,,iii4 ,such is the ordinary method for the treatment of guano2 but ,mr4 ,rylands' mode of proceeding with ordinary ,diatomace 7before given7 will be found equally successful with these deposits4 ,the fossil ,infusoria 7as they were formerly called7 are now termed ,diatomace1 and are found in various parts of the world--8,bermuda earth10 8,berg-mehl0 from ,norway1 deposit from ,mourne ,mountain in ,ireland1 c4 ,they are found in immense quantities1 and afford the microscopist innumerable objects4 ,the same treatment as that usually employed for the ,diatomace must be followed with these deposits1 but as they are sometimes obtained in hard masses1 disintegration is first necessary4 ,to effect this1 they are usually boiled for a short time in diluted liquor potass1 which will soon cause the mass to fall into a mud-like deposit4 ,water must then be immediately added1 in order that all further action of the liquor potass may be stopped1 otherwise the objects searched for will be dissolved4 ,for this reason it is necessary to understand what substance is being dealt with1 because some deposits are much finer and acted upon more readily than others4 ,in mounting these objects1 some are so delicate that they are almost invisible when balsam is used with them2 they are therefore usually mounted dry4 ,others1 however1 are much coarser1 and may be mounted in balsam like the ,diatomace mentioned in ,chapter ,,iii4 ,the common ,infusoria cannot be mounted dry with any great success1 though a few may be placed upon the glass slide and allowed to dry naturally1 when their characters will be very well shown4 ,to obtain anything like a natural appearance1 they must be put up in fluid as in ,chapter ,,iv4 ,next to the ,diatomace1 no class of microscopic objects has been more looked into of late than the ,foraminifera4 ,these animals are almost all marine1 having a jelly-like body enclosed in one or more chambers of shell generally composed of carbonate of lime4 ,the shells are made with minute orifices1 through which the pseudopodia 7false feet7 are extended by which the animal is enabled to lay hold of anything and draw itself along4 ,from the possession of these orifices they derive their name1 as foramen means a door or opening4 ,they have been found in every depth of sea hitherto sounded1 each depth being abundant in certain species2 the lowest beds containing the greatest number of specimens1 though with less variation of kinds4 ,in chalk they are found in a fossil state1 and may readily be shown 7see ,chapter ,,iii472 in limestone and other hard stones they are abundant1 and some mountains are composed principally of these shells4 ,the methods of obtaining ,foraminifera are various4 ,many may be found upon seaweeds1 which should always be examined as soon as possible after gathering4 ,they are found in masses upon some coasts where the waves have carried and left them2 but they are to be found the most abundantly in sand or mud dredged from the bottom of the sea4 ,they must1 however1 be cleansed and separated from the mass of impurity with which they are usually mixed4 ,this may be done in various ways1 according to the nature of the accompanying matter4 ,if sand alone1 as is frequently the case1 the whole mass must be thoroughly dried1 and then stirred up in clean water4 ,the sand will soon subside by its own weight1 but the chambers of the ,foraminifera1 being filled with air1 will float upon the surface1 and may be skimmed off4 ,there is1 however1 one objection to this mode of proceeding--some of these objects are so minute1 the chambers containing comparatively so small a quantity of air1 that they sink and are cast away with the refuse sand4 ,on this account it is preferable to take the trouble of searching certain soundings under the microscope1 using the camel-hair pencil1 or some other contrivance before mentioned1 to extract those objects which are required4 ,to clean the ,foraminifera1 ,professor ,williamson advises to transfer the specimens to an evaporating dish containing a weak solution of caustic potash4 ,this must be boiled for 8some moments10 when the organic matter will be entirely dissolved1 and the calcareous shells left free from impurity4 ,they must now be well washed in water1 so that all alkaline matter may be entirely got rid of4 ,if the specimens are in mud1 we must proceed in a different way3--,stir up the whole mass in water1 and allow it to stand until the heavier portion has sunk to the bottom2 the water may then be poured off and examined to see if there are any objects contained in it4 ,this process must be repeated until the water comes off quite clear1 when 7if the search is for ,foraminifera only7 the solution of caustic potash may be used as before mentioned4 ,however the soundings1 c41 are cleaned1 it is necessary to assort them under the microscope with the camel-hair pencil or other contrivance1 as it is impossible to obtain them fit for mounting without undergoing this process4 ,the sea soundings taken by order of ,government are drawn from the bottom in a kind of apparatus ingeniously made for the purpose1 and the sand1 mud1 c41 are brought up in their original state4 ,common soundings1 however1 are taken by lowering a heavy piece of lead coated with tallow1 which consequently brings up a small portion of the matter from the bottom4 ,mr4 ,george ,mosley1 the late ,secretary of the ,manchester ,microscopic ,society1 obtained numbers of the 8scrapings0 from the sounding leads4 ,to make any use of these it is1 of course1 necessary to free them from all traces of the tallow4 ,mr4 ,dancer places the sounding in a basin and pours boiling water upon it1 which causes the melted grease to rise to the surface4 ,when cold1 this may be removed1 and the water carefully decanted4 ,the operation may be repeated until no grease appears1 when the water may be withdrawn and liquor ammoni used1 which will form a soapy solution with any remaining grease4 ,this must be treated with hot water for the final washing4 ,care must be taken lest the finer forms be carried away in decanting the washing liquid4 ,should it be wished to make certain as to this point1 each washing should be examined under the microscope4 ,in some cases the process of ,mr4 ,dancer will prove sufficient4 ,mr4 ,dale1 however1 gives a method of accomplishing the same result1 which is much more readily completed2 and as the results cannot be found fault with1 ,i will here give it in full3--,it is now well known that one of the products obtained from the naphtha of coal-tar is a volatile1 oily substance1 termed benzole 7or1 by ,french chemists1 benzine71 whose boiling-point1 when pure1 is about #ahj ,fahrenheit1 which is a perfect solvent for fatty substances4 ,in a capsule1 previously warmed on a sand-bath1 ,mr4 ,dale mixes with the tallow soundings benzole1 whose boiling-point may be about #bjj1 until sufficiently diluted so as to run freely1 pressing the lumps with a glass rod until thoroughly mingled2 the solution and its contents are then poured into a paper filter1 placed in a glass funnel2 the capsule is again washed with benzole1 until the whole of the gritty particles are removed into the filter4 ,a washing-bottle is then supplied with benzole1 and the contents of the filter washed to the bottom until that liquid passes off pure1 which may be tested by placing a drop from the point of the funnel on a warm slip of glass or bright platinum1 when1 if pure1 the benzole will evaporate without residue or tarnish2 if grease be present1 the washings must be continued until they are free from it4 ,after rinsing through weak acid1 or alcohol1 for final purification1 the calcareous forms will be ready for mounting4 ,the filter and its contents may be left to dry spontaneously1 when the latter can be examined by the microscope4 ,should time be an object1 rapid drying may be effected by any of the usual methods2 one of which1 recommended by ,mr4 ,dale1 is to blow a stream of hot air through a glass tube held in the flame of a ,bunsen's burner4 ,the lower the boiling-point of the benzole1 the more readily can the specimens be freed from it4 ,a commoner quality may be used1 but it is more difficult to dry afterwards4 ,pure benzole being costly1 this may appear an expensive process2 but1 with the exception of a trifling loss by evaporation1 the whole may be recovered by simple distillation4 ,the mixture of tallow and benzole being placed in a retort in a hot-water1 a steam1 or a sand bath1 the benzole will pass into the receiver1 and the tallow or other impurities will remain in the retort4 ,when the whole of the benzole has distilled over1 which is ascertained by its ceasing to drop from the condenser1 the heat is withdrawn and the retort allowed to cool before the addition of fresh material4 ,half a dozen to a dozen filters1 each with its specimen1 can be in process at the same time2 and the distillation of the recovered benzole progresses as quickly as the filtration1 which was practically proved on the occasion named4 ,great caution in the use of benzole is to be taken in the approach of lights to the inflammable vapour4 ,after the ,foraminifera and calcareous forms have been removed1 the residue may be treated with acids and levigation in the usual manner1 to obtain siliceous forms and discs1 if there are any present2 but to facilitate their deposition1 and to avoid the loss of any minute atoms suspended in the washings1 ,i would suggest the use of filtration4 ,the conical filter is unsuitable1 as the particles would spread over too great a surface of paper2 but glass tubes open at both ends 7such as broken test-tubes7 will be found to answer1 the broad end covered with filtering paper1 and over that a slip of muslin tied on with a thread to facilitate the passage of the water and prevent the risk of breaking the paper4 ,suspend the tube over a suitable vessel through a hole cut in thin wood or cardboard1 pour in the washings which can be thus filtered and then dried4 ,the cloth must be carefully removed1 the paper cut round the edges of the tube1 and the diatoms on the paper disc may be removed by a camel-hair pencil or otherwise1 ready for mounting4 ,thus many objects may be preserved which would be either washed away or only be obtained by a more tedious process4 ,such is ,mr4 ,dale's method of cleaning the soundings from the tallow1 and as it thoroughly accomplishes its end1 and is alike effective and not injurious to ,foraminifera and diatoms1 it may be safely recommended4 ,the weak solution of caustic potash before advised for ,foraminifera1 must not be used where it is desired to preserve the diatoms1 as they would certainly be injured1 or destroyed altogether1 if this agent were employed4 ,in fixing the ,foraminifera upon the slide1 no better plan can be followed than the 8dry cells0 and gum recommended in the early parts of this chapter4 ,owing to their thickness and composition1 most of them are opaque objects only2 but they are exquisitely beautiful1 and require no particular care1 except in allowing the cell1 c41 to be perfectly dry1 when the cover is placed upon it1 or the damp will certainly become condensed upon the inner side1 and the examination seriously interfered with4 ,many of the ,foraminifera require cutting into sections if it is wished to examine the internal structure1 c41--8decalcifying0 is also desirable in some cases2--both of these processes will be found described at length in the chapter on ,sections and ,dissection4 ,when more than one specimen of some particular shell is obtained1 it is better to place them upon the slide in different positions1 so as to show as much of the structure as possible4 ,i will conclude this subject by quoting a passage from ,t4 ,rymer ,jones3--8,it is1 therefore1 by no means sufficient to treat these shells as ordinary objects by simply laying them on a glass slide1 so as to see them only from one or two points of view2 they must be carefully examined in every direction1 for such is the diversity of form that nothing short of this will be at all satisfactory4 ,for this purpose1 they should be attached to the point of a fine needle1 so that they may be turned in any direction1 and examined by reflected light condensed upon them by means of a lens or side reflector4 ,in many of the thick-shelled species it will be necessary to grind them down on a hone see ,chapter ,v4 before the number and arrangement of the internal chambers is discernible2 and in order to investigate satisfactorily the minuti of their structure1 a variety of sections1 made in various ways1 is indispensable40 ,plants afford an almost inexhaustible treasury for the microscope1 and many of them show their beauties best when mounted dry4 ,when any of these also are to be mounted1 care must be taken that they are thoroughly dry1 otherwise the damp will certainly arise in the cell1 and injure the object2 and it may be here mentioned that long after a leaf has every appearance of dryness1 the interior is still damp1 and no way can be recommended of getting rid of this by any quicker process than that effected by keeping them in a warm room1 as many leaves1 c41 are utterly spoiled by using a hot iron or other contrivance4 ,the safest way is to press them gently betwixt blotting-paper1 which may be removed and dried at short intervals2 and though this may appear a tedious operation1 it is a safe one4 ,on the surface of the leaves1 hairs and scales of various and very beautiful forms are found1 most of which display their beauties best when removed from the leaf1 and used with the polarizer4 ,these will be noticed in another place2 but a portion of the leaf should always be prepared in its natural form1 to show the arrangement of the hair or scales upon it2 which must almost invariably be mounted dry when used for this purpose4 ,many of them require very delicate handling4 ,the epidermis1 or1 as it is by some termed1 the cuticle1 is the outer skin which lies upon the surface of the leaves and other parts of most plants4 ,this is composed of cells closely connected1 often bearing the appearance of a rude network4 ,in many plants1 by scraping up the surface of the leaf1 a thin coating is detached1 which may be torn off by taking hold of it with the forceps4 ,the piece may then be washed and floated upon a glass slide1 where1 on drying1 it will be firmly fixed1 and may usually be mounted dry4 ,amongst the most beautiful and easily prepared of these may be mentioned the petal of the geranium1 the cells of which are well defined and amongst the most interesting4 ,closely connected with the leaves are the ,,anthers and ,,pollen1 of which a great number are beautiful and interesting subjects for the microscopist4 ,the mallow tribe will furnish some exquisite objects1 bearing the appearance of masses of costly jewels4 ,these are usually dried with pressure1 but the natural form may be more accurately preserved by allowing them to dry as they are taken from the flower1 with no interference except thoroughly protecting them from all dust4 ,sometimes the anther is divided1 so that the cell required to receive them may be of as little depth as possible4 ,the common mallow is a beautiful object1 but ,i think the lavatera is a better1 as it shows the pollen chambers well1 when dried unpressed4 ,the pollen is often set alone1 and is well worth the trouble1 as it then admits of more close examination4 ,often it is convenient to have the anther and pollen as seen in nature on one slide1 and the pollen alone upon another4 ,the former should be taken from the flowers before their full development is attained1 as if overgrown they lose much of their beauty4 ,some pollens are naturally so dark that it is necessary to mount them in ,canada balsam or fluid1 as described in other places2 but they are better mounted dry when they are not too opaque4 ,here1 too1 we may also mention the ,,seeds of many plants as most interesting1 and some of them very beautiful1 objects1 requiring for the greater part but a low power to show them4 ,most of these are to be mounted dry1 as opaque objects1 in cells suited to them1 but some are best seen in balsam1 and will be mentioned in ,chapter ,,iii4 ,the ,,corallines1 many of which are found on almost every coast1 afford some very valuable objects for the microscope4 ,they must be well washed when first procured1 to get rid of all the salts in the sea-water1 dried and mounted in cells deep enough to protect them from all danger of pressure1 as some of them are exceedingly fragile4 ,the white ivory appearance which some of them present is given to them by an even covering of carbonate of lime2 and should it be desired to examine the structure of these more closely1 it may be accomplished by keeping them for some time in vinegar or dilute muriatic acid1 which will remove the lime and allow of the substance being sliced in the same way as other ,alg4 78,micrographic ,dictionary10 p4 #ahc47 ,,the ,,scales ,,of ,,insects4--,the fine dust upon the wings of moths and butterflies1 which is so readily removed when handled carelessly1 is what is generally called scales4 ,to these the wing owes the magnificent colours which so often are seen upon it2 every particle being what may be termed a distinct flat feather4 ,how these are placed 7somewhat like tiles upon a roof7 may be easily seen in the wing of any butterfly1 a few being removed to aid the investigation4 ,the form of them is usually that of the 8battledore0 with which the common game is played1 but the handle or base of the scale is often short1 and the broad part varies in proportionate length and breadth in different specimens4 ,the markings upon these also vary1 some being mostly composed of lines running from the base to the apex1 others reminding us of network--bead-like spots only are seen in some--indeed1 almost endless changes are found amongst them4 ,these scales are not confined to butterflies and moths1 nor indeed to the wings of insects4 ,the different gnats supply some most beautiful specimens1 not only from the wings1 but also from the proboscis1 c42 whilst from still more minute insects1 as the podura1 scales are taken which were at one time esteemed as a most delicate test4 ,the gorgeous colours which the diamond beetles also show when under the microscope are produced by light reflected from minute scales with which the insects are covered4 ,in mounting these objects for the microscope it is well to have the part of the insect from which the scales are usually taken as a separate slide1 so that the natural arrangement of them may be seen4 ,this is easily accomplished with the wings of butterflies1 gnats1 c42 as they require no extraordinary care4 ,in mounting the scales they may be placed upon slides1 by passing the wings over the surface1 or by gently scraping the wing upon the slide1 when they must be covered with the thin glass4 ,of course1 the extreme tenuity of these objects does away with the necessity of any cell excepting that formed by the gold-size or other cement used to attach the cover4 ,the scales of the podura should be placed upon the slide in a somewhat different manner4 ,this insect is without wings1 and is no longer than the common flea4 ,it is often found amongst the sawdust in wine-cellars1 continually leaping about by the aid of its tail1 which is bent underneath its body4 ,dr4 ,carpenter says3--8,podur may be obtained by sprinkling a little oatmeal on a piece of black paper near their haunts2 and after leaving it there for a few hours1 removing it carefully to a large glazed basin1 so that1 when they leap from the paper 7as they will when brought to the light71 they may fall into the basin1 and may thus separate themselves from the meal4 ,the best way of obtaining their scales1 is to confine several of them together beneath a wine glass inverted upon a piece of fine smooth paper2 for the scales will become detached by their leaps against the glass1 and will fall upon the paper40 ,these scales are removed to the slide1 and mounted as those from the gnats1 c4 ,when the podura has been caught without the aid of the meal1 it may be placed upon the slide1 under a test-tube1 or by any other mode of confinement1 and thus save the trouble of transfer from the paper before mentioned4 ,another method is to seize the insect by the leg with the forceps and drag it across the slide1 when a sufficient quantity of scales will probably be left upon it4 ,these scales are usually mounted 8dry20 but ,hogg recommends the use of ,canada balsam 7,chapter ,,iii47 as rendering their structure more definite when illuminated with ,wenham's parabolic reflector4 ,some advise other methods1 which will be mentioned in ,chapter ,,iv4 ,as most insects when undissected are mounted in ,canada balsam1 the different modes of treatment which they require will be stated in another place4 ,in mounting blood of any kind to show the corpuscles1 or1 as they are often called1 globules1 which are round or oval discs1 it is but necessary to cover the slide on the spot required with a coating as thin as possible and allow it to dry before covering with the thin glass4 ,there is a slight contraction in the globules when dried1 but not enough to injure them for the microscope4 ,the shape of these varies in different classes of animals1 but the size varies much more1 some being many times as large as others4--,some of the larv skins are beautiful objects2 but1 like many sections of animal and other fragile matter1 are difficult to extend upon the slide4 ,this difficulty is easily overcome by floating the thin object in clear water1 immersing the slide and when the object is evenly spread gently lifting it4 ,allow it then to dry by slightly raising one end of the slide to aid the drainage1 and cover with the thin glass as other objects4 ,the tails and fins of many small fish may be mounted in a similar manner1 and are well worth the trouble4 ,a few objects which are best shown by mounting dry may be here mentioned as a slight guide to the beginner1 though some of them have been before noticed2--many of the ,foraminifera as elsewhere described4 ,some crystals are soluble in almost any fluid or balsam1 and should be mounted dry2 a few1 however1 deliquesce or effloresce1 which renders them worthless as microscopic objects4 ,the wings of butterflies and gnats1 as before noticed1 afford many specimens wherewith to supply the cabinet of the young student4 ,a great variety also may be found amongst the ferns2 indeed1 these alone will afford the student occupation for a long time4 ,on the under-side of the leaves are the reservoirs for the 8spores10 which in many instances somewhat resemble green velvet1 and are arranged in stripes1 round masses1 and other forms4 ,the spores are usually covered with a thin skin termed the indusium1 which is curiously marked in some specimens1 often very like pollen-grains4 ,the manner in which these spores with all their accompaniments are arranged1 their changes and developments afford almost endless subjects for study2 different ferns presenting us with many variations in this respect totally invisible without the aid of the microscope4 ,the hymenophyllums 7of which two only belong to ,england7 are particularly interesting1 and the structure of the leaves when dried makes them beautiful objects1 often requiring no balsam to aid their transparency4 ,portions of the fronds of ferns should be mounted as opaque objects1 after having been dried between blotting paper1 when they are not injured by pressure2 but care must be taken to gather them at the right time1 as they do not show their beauty before they are ripe1 and if over-ripe the arrangement of the spores1 c41 is altered4 ,the spores may be mounted as separate objects in the same manner as pollen1 before-mentioned1 and are exquisitely beautiful when viewed with a tolerably high power4 ,the number of foreign ferns now cultivated in this country has greatly widened the field for research in this direction2 and it may also be mentioned that the under-sides of many are found to be covered with 8scales0 of very beautiful forms4 ,a small piece of the frond of one of these may be mounted in its natural state1 but the removal of the 8scales0 for examination by polarized light will be described in another place4 ,the mosses also are quite a little world1 requiring but a low power to show their beauties4 ,the leaves are of various forms1 some of which resemble beautiful net-work2 the 8urns0 or reservoirs for the spores1 however1 are perhaps the most interesting parts of these objects1 as also of the 8liverworts0 which are closely allied to the mosses4 ,these 8urns0 are generally covered by lids1 which fall off when the fruit is ripe4 ,at this period they are well fitted for the microscope4 ,the common screw-moss may be found in great abundance1 and shows this denudation of the spores very perfectly4 ,many of these may be easily dried without much injury1 but they should also be examined in their natural state4 ,the student should not omit from his cabinet a leaf of the nettle and the allied foreign species1 the mystery of which the microscope will make plain4 ,the hairs or stings may also be removed1 and viewed with a higher power than when on the leaf1 being so transparent as to require no balsam or other preservative4 ,there are few more interesting objects than the raphides or plant-crystals4 ,these are far from being rare1 but in some plants they are very minute1 and consequently require care in the mounting1 as well as a high magnifying power to render them visible2 in others they are so large that about twenty-five of them placed point to point would reach one inch4 ,some of these crystals are long and comparatively very thin1 which suggested the name 7raphis1 a needle72 others are star-like1 with long and slender rays2 while others again are of a somewhat similar form1 each ray being solid and short4 ,if the stem of rhubarb1 or almost any of the hyacinth tribe1 be bruised1 so that the 8juice0 may flow upon the slide1 in all probability some of these crystals will be found in the fluid4 ,to obtain them clean1 they must be freed from all vegetable matter by maceration4 ,after this they must be thoroughly washed and mounted 8dry40 ,they are also good polarizing objects1 giving brilliant colours2 but when used for this purpose they must be mounted as described in ,chapter ,,iii4 ,a few plants which contain them may be mentioned here4 ,the ,cactace are very prolific2 the orchids1 geraniums1 tulips1 and the outer coating of the onion1 furnish the more unusual forms4 ,the ,fungi are generally looked upon as a very difficult class of objects to deal with1 but amongst them some of the most available may be found4 ,the forms of many are very beautiful1 but are so minute as to require a high magnifying power to show them4 ,the mould which forms on many substances is a fungus1 and in some cases may be dried and preserved in its natural state4 ,a friend of mine brought me a rose-bush completely covered with a white blight4 ,this was found to be a fungus1 which required a high magnifying power to show it4 ,being a very interesting object1 it was desirable to preserve it1 and this was perfectly effected without injury to the form by simply drying the leaf in a room usually occupied4 ,amongst the fungi are many objects well worth looking for1 one of which is the ,diacha elegans4 ,this1 the only species1 says the 8,micrographic ,dictionary10 is found in ,england upon the living leaves of the lily-of-the-valley1 c4 ,these little plants grow in masses1 reminding one of mould1 to a height of a quarter of an inch1 and each 8stem0 is covered with a sheath1 in shape somewhat like an elongated thimble4 ,when ripe the sheath falls off and reveals the same shaped column1 made up of beautifully fine net-work1 with the spores lying here and there4 ,this dries well1 and is a good object for the middle powers4 ,amongst the fungi the blights of wheat and of other articles of food may be included4 ,many of them may be mounted 8dry20 others1 however1 cannot be well preserved except in liquids1 and will be referred to in ,chapter ,,iv4 ,amongst the zoophytes and sea-mats1 commonly called 8sea-weeds10 may be found many very interesting objects to be mounted 8dry40 ,when this mode of preservation is used1 it is necessary that all the sea-salt be thoroughly washed from them4 ,as they are1 however1 most frequently mounted in balsam or liquid1 they will be more fully noticed in other places4 ,the scales of fishes are generally mounted 8dry0 when used as ordinary objects2 but for polarized light1 balsam or liquid must be used1 as noticed in ,chapter ,,iii4 ,the variety and beauty of these are quite surprising to the novice4 ,it is also very interesting to procure the skin of the fish when possible1 and mount it on a separate slide to show how the scales are arranged4 ,the sole is one of the most unusual forms1 the projecting end of each scale being covered with spines1 which radiate from a common centre1 while those at the extremity are carried out somewhat resembling the rays of a star4 ,one of the skates has a spine projecting from the centre of each scale1 which is a very curious opaque object1 especially when the skin is mounted in the manner described4 ,the perch1 roach1 minnow1 and others of the common fishes give the student good objects for his cabinet1 and may be procured without difficulty4 ,insects which are very transparent1 or have the 8metallic lustre0 with which any medium would interfere1 are mounted 8dry40 ,the diamond-beetle1 before mentioned1 is a splendid example of this2 the back is generally used1 but the legs1 showing the curious feet1 are very interesting objects4 ,indeed1 amongst the legs and feet of insects there is a wide field of interest4 ,when they are of a 8horny0 nature1 it is best to dry them in any form preferred1 but to use no pressure2 when1 however1 they are wanted flat1 so as to show the feet1 c41 extended1 they must be dried with a gentle pressure betwixt blotting-paper if possible4 ,but this will be treated more fully in ,chapter ,,iii4 ,the eyes of insects are sometimes allowed to dry in their natural shape1 and mounted as opaque objects2 but generally they are used as transparencies in balsam or liquid1 so the description of the treatment which they require will be deferred to ,chapter ,,iii4 ,hairs1 when not too dark1 are sometimes transparent enough when mounted dry1 but are usually mounted in balsam4 ,these also will be more fully noticed in another place4 ,these are a few of the objects which are often mounted dry1 but some of them should be shown in balsam or liquid also1 and there is much difference of opinion as to the best way of preserving others4 ,this1 however1 is explained by the transparency which the balsam gives interfering with one property of the object and yet developing another which would have remained invisible if preserved dry4 ,the only method of overcoming this difficulty is to keep the object mounted in both ways1 which is comparatively little trouble4 ,i may here mention that many prefer the lieberkuhn for the illumination of opaque objects2 and a good background is gained by putting upon the under side of the slide1 immediately beneath the object1 a spot of black varnish1 which does not interfere materially with the light4 ,,chapter ,,iii4 ,,mounting ,,in ,,canada ,,balsam4 ,the nature and use of this substance has been before spoken of1 so the method of working with it may be at once described4 ,perfect dryness of the objects is1 if possible1 more necessary in this mode of mounting than any other1 as dampness remaining in the object will assuredly cause a cloudiness to make its appearance in a short time after it is fixed4 ,where pressure does not injure the specimens1 they are most successfully treated when first dried betwixt the leaves of a book1 or in any other way which may prove most convenient1 as noticed in ,chapter ,,ii4 ,before describing the methods of proceeding with any particular objects1 general rules may be given which should be observed in order to succeed in this branch of mounting4 ,as the object is to be thoroughly immersed in the balsam1 it is evident that when it has once been covered1 so it must remain1 unless we again free it by a process hereafter mentioned1 which is very troublesome2 and on this account there must be nothing whatever in the balsam except the object4 ,the inexperienced may think this an unnecessary caution2 but the greatest difficulty he will meet with is to get rid of minute bubbles of air1 perhaps invisible to the naked eye1 which appear like small globules when under the microscope1 and render the slide unsightly1 or even worthless4 ,ten objects out of eleven contain air1 or at least are full of minute holes which are necessarily filled with it2 so that if they should be immersed in any liquid of thick consistency1 these cells of air would be imprisoned1 and become bubbles4 ,the air1 then1 must be got rid of1 and this is usually accomplished by soaking for some time in turpentine1 the period required differing according to the nature of the object4 ,in some cases1 the turpentine acts upon the colour1 or even removes it altogether1 so that it must be watched carefully4 ,often1 however1 this is an advantage1 as where the structure alone is wanted1 the removal of the colouring matter renders it more transparent4 ,there are objects1 however1 which retain the air with such tenacity that soaking alone will not remove it4 ,if these will bear heat without being injured1 they may be boiled in turpentine1 or even in balsam1 when the air will be partly or totally expelled4 ,but where heat is objectionable1 they must be immersed in the turpentine1 and so submitted to the action of the air-pump4 ,even with this aid1 sometimes days are required to accomplish it perfectly1 during which time the air should be exhausted at intervals of five or six hours1 if convenient1 and the objects turned over now and then4 ,sometimes the objects are so minute that it is impossible to submit them to any soaking1 and in this case they must be laid upon the slide at once1 and the turpentine applied to them there4 ,but it must not be forgotten that there are some few which are much better mounted in such a way that the balsam may thoroughly surround1 and yet not penetrate1 the substance more than necessary4 ,sections of teeth are amongst these1 which will be noticed in another place1 and some insects 7see ,dr4 ,carpenter7 when required to show the 8ramifications of the trache40 ,having freed the object1 then1 from these two enemies--dampness and air--we must proceed to mount it4 ,the slide must first be cleaned2 then on the centre a quantity of balsam must be placed with a bluntly-pointed glass rod1 according to the size of the object about to be mounted4 ,to this a slight heat must be applied1 which will cause any bubbles to rise from the surface of the slide1 so that they may be readily removed with a needle4 ,the object should be freed from all air by steeping in turpentine1 as before described1 and then from superfluous liquid by a short drainage1 and carefully laid upon1 or where it is practicable thrust into1 the balsam1 prepared on the slide as above4 ,in the former case1 or where the balsam has not totally covered the object1 a small quantity must be taken1 warmed1 and dropped upon it1 and any bubbles removed by the needle as before4 ,to cover this1 the thin glass must be warmed1 and beginning at one side1 allowed to fall upon the balsam1 driving a small 8wave0 before it1 and thus expelling any bubbles which may remain4 ,this is quite as safely performed 7if not more so7 by making a solution of balsam in turpentine of the consistency of thick varnish4 ,the thin glass cover may be slightly coated with this1 and will then be much less liable to imprison any air1 which frequently happens when the cover is dry4 ,bubbles1 however1 will sometimes make their appearance in spite of all care2 but when the object is comparatively strong1 they may be removed by keeping the slide rather warm1 and working the cover a little1 so as to press them to one side1 when they should be immediately removed with a needle point1 otherwise they are again drawn under4 ,where the slide requires keeping warm for any length of time1 a hot-water bath is sometimes made use of1 which is simply a flat tin1 or other metal case1 with a mouth at the side1 that when the hot water is introduced it may be closed up1 and so retain its warmth for a long time4 ,in working1 the slide is laid upon it1 and so admits of longer operations1 when required1 without growing cold4 ,sometimes a spirit-lamp is placed under it to keep up an equal heat through excessively long processes4 ,where the time required1 however1 is but short1 a thick brass plate is sometimes used 7see ,chapter ,i471 which is heated to any degree that is required1 and the slide placed upon it4 ,some objects1 which are so thin that they are usually floated upon the slide1 as before stated1 require no steeping in turpentine or other liquid4 ,these are best mounted by covering with a little diluted balsam1 and after this has had time to penetrate the substance1 ordinary balsam is laid upon it1 and the slide finished in the usual manner4 ,i have stated that the balsam is usually applied to the slide and objects with a 8bluntly-pointed glass rod20 but for the purpose of drawing the balsam from the bottle1 and conveying it to the desired place1 ,dr4 ,carpenter uses a glass syringe with a free opening4 ,these are his instructions3--8,this 7the syringe7 is most readily filled with balsam1 in the first instance1 by drawing out the piston1 and pouring in balsam previously rendered more liquid by gentle warmth2 and nothing else is required to enable the operator at any time to expel precisely the amount of balsam he may require1 than to warm the point of the syringe1 if the balsam should have hardened in it1 and to apply a very gentle heat to the syringe generally1 if the piston should not then be readily pressed down4 ,when a number of balsam objects are being mounted at one time1 the advantage of this plan in regard to facility and cleanliness 7no superfluous balsam being deposited on the slide7 will make itself sensibly felt40 ,when the 8mounting0 is thus far accomplished1 the outer 8wall0 of balsam may be roughly removed after a few hours have elapsed2 but great care is necessary lest the cover be moved or interfered with in any way4 ,in this state it may be left for the final cleansing until the balsam becomes hard1 which takes place sooner or later1 according to the degree of warmth it has been subjected to4 ,a mantel-piece1 or some place about equal to it in temperature1 is the best suited to this purpose2 and when the requisite hardness is attained1 it may be proceeded with as follows3--,with a pointed knife the balsam must be scraped away1 taking care that the thin glass be not cracked by the point getting under it4 ,if used carefully1 the knife will render the slide almost clean2 but any minute portions which still adhere to the glass must be rubbed with linen dipped in turpentine or spirit4 ,if the balsam is not very hard1 these small fragments are readily removed by folding a piece of paper tightly in a triangular form with many folds1 and damping the point with which the glass is rubbed4 ,as the paper becomes worn with the friction1 the balsam will be carried off with it4 ,in some cases ,i have found this simple expedient very useful4 ,sometimes the object to be mounted is of such a thickness as to require a cell4 ,for this purpose glass rings are used 7as described in ,chapter ,,iv471 and filled with balsam4 ,the best mode of doing this is thus described by ,mr4 ,t4 ,s4 ,ralph in the ,microscopic ,journal3--8,the question was asked me when ,i was in ,england1 if ,i knew how to fill a cell with ,canada balsam and leave behind no air-bubbles8 ,i replied in the negative2 but now ,i can state how to accomplish this4 ,fill the cell with clear spirit of turpentine1 place the specimen in it1 have ready some balsam just fluid enough to flow out of the bottle when warmed by the hand2 pour this on the object at one end1 and1 gradually inclining the slide1 allow the spirit of turpentine to flow out on the opposite side of the cell till it is full of balsam2 then take up the cover1 and carefully place upon it a small streak of ,canada balsam from one end to the other4 ,this1 if laid on the cell with one edge first1 and then gradually lowered until it lies flat1 will drive all the air before it1 and prevent any bubbles from being included in the cell4 ,it can be easily put on so neatly as to require no cleaning when dry4 ,if the cover is pressed down too rapidly1 the balsam will flow over it1 and require to be cleaned off when hardened1 for it cannot be done safely while fluid at the edges40 ,sometimes with every care bubbles are enclosed in the balsam1 injuring objects which are perhaps rare and valuable4 ,the whole slide must then be immersed in turpentine until the cover is removed by the solution of the balsam2 and the object must be cleansed by a similar steeping4 ,it may then be remounted as if new in the manner before described4 ,the balsam and chloroform described in ,chapter ,i4 is thus used2 and where the object is thin1 the mounting is very easily accomplished4 ,when the object is laid upon the slide with a piece of glass upon it1 and the balsam and chloroform placed at the edge of the cover1 the mixture will gradually flow into the space betwixt the glasses until the object is surrounded by it1 and the unoccupied portion filled4 ,the chloroform will evaporate so quickly that the outer edge will become hard in a very short time1 when it may be cleaned in the ordinary way4 ,sometimes the balsam is dissolved in the chloroform without being first hardened2 but this is only to render it more fluid1 and so give the operator less chance of leaving bubbles in the finished slide1 as the thicker the medium is1 the more difficult is it to get rid of these intruders4 ,it has been before mentioned that some have objected to chloroform and balsam1 believing that it became clouded after a certain time4 ,perhaps this may be accounted for in part by the fact that almost all objects have a certain amount of dampness in them4 ,others are kept in some preservative liquid until the time of mounting1 and these liquids generally contain certain salts 7,chapter ,,iv474 ,if this dampness1 as well as all traces of these salts1 however small1 are not totally removed--the former by drying1 the latter by repeated washings--the addition of chloroform will render the balsam much more liable to the cloudiness than when balsam alone was used1 as before mentioned4 ,this mode of employing the balsam1 however1 will not be always applicable1 as chloroform acts upon some substances which balsam alone does not4 ,some salts are even soluble in it1 the crystals disappearing after a few days or weeks1 whereas in the balsam alone they are quite permanent4 ,experience is the only guide in some cases1 whilst in others a little forethought will be all that is required4 ,the particular methods used for certain objects may be now entered upon4 ,many of the ,diatomace and fossil ,infusoria1 as they are sometimes termed1 are mounted dry1 and cleaned in the way described in ,chapter ,,ii4 ,others are almost always placed in balsam1 except where they are intended to be used with the lieberkuhn and dark background1 by which means some of them are rendered exquisitely beautiful4 ,the usual way of mounting them in balsam is as follows3--,take a drop of the water containing them1 place it upon the slide1 and evaporate over the lamp1 whilst with a needle they may be dispersed over any space desired4 ,when they are thoroughly dry1 drop a little balsam on one side1 and exclude the bubbles4 ,the slide may then be warmed to such a degree that the balsam1 by lifting the glass at one end1 will be carried over the specimens1 which may then be covered with thin glass1 made warm as before described4 ,where the objects are quite dry1 and loose upon the glass1 it requires great care in placing the cover upon them1 otherwise they are forced to one edge1 or altogether from under it1 in the wave of the balsam4 ,for this reason1 ,professor ,williamson adds a few drops of gum-water to the last washing1 which causes them to adhere sufficiently to the glass to prevent any such mishap4 ,mr4 ,t4 ,g4 ,rylands' method differs in some degree from the above1 and is1 to use his own words1 as follows3--,thick balsam is preferable1 and the burnt covers 7see ,chapter ,,ii47 to be mounted are laid in a convenient position with the diatoms upwards4 ,the slides required having been carefully cleaned and marked on the under side with a ring of ink1 by the aid of a turntable about half an inch in diameter to point out the centre1 a drop of benzole is applied by a large pin to the diatoms on the cover1 so as to exclude the air from the valves and frustules4 ,the slide is then held over the lamp1 and when warm1 a sufficiently large drop of balsam is put upon it1 and heated until it begins to steam4 ,if small bubbles appear1 a puff of breath removes them4 ,the slide being held slightly inclined from the operator1 and the drop of balsam becoming convex at its lower edge1 the cover is brought in contact with it at that point1 gradually laid down1 pressed with the forceps1 and brought to its central position4 ,when cool the superfluous balsam 7if any7 is removed with a heated knife-blade1 the slide cleaned with a little turpentine1 and finished by washing in a hand-basin with soap and water4 ,in this process there is no delay if the balsam be sufficiently thick1 as the slide may be cleaned off almost before it is cold4 ,it is now well known that from common chalk it is an easy matter to obtain interesting specimens of ,foraminifera4 ,scrape a small quantity of chalk from the mass and shake it in water2 leave this a few minutes1 pour the water away and add a fresh quantity1 shake up as before1 and repeat two or three times4 ,take a little of the residue1 and spread it upon the slide1 and when quite dry add a little turpentine4 ,when viewed with a power of two hundred and fifty diameters this will generally show the organisms very well4 ,if it is desired to preserve the slides1 they may be then mounted in ,canada balsam4 ,mr4 ,guyon1 in 8,recreative ,science10 observes that the accumulation of the powder1 by the action of the rain or exposure to the atmospheric action1 at the foot or any projection of the chalk cliffs1 will afford us better specimens than that which is 8scraped10 as the organisms are less broken in the former4 ,when the ,foraminifera are of a larger size1 though transparent enough to be mounted in balsam1 the air must be first expelled from the interior1 otherwise the objects will be altogether unsatisfactory4 ,to accomplish this they must be immersed in turpentine and submitted to the action of the air-pump4 ,so difficult is it to get rid of this enemy that it is often necessary to employ three or four exhaustions1 leaving them for some time under each4 ,when all air has given place to the turpentine1 they must be mounted in the ordinary way4 ,of all objects which are commonly met with1 few are such general favourites as the ,,polycystin1 and deservedly so4 ,their forms are most beautiful1 and often peculiar--stars varying in design1 others closely resembling crowns2 the ,astromma ,aristotelis like a cross1 and many whose shapes no words could describe4 ,the greater part1 perhaps1 of those which are usually sold1 is from the rocky parts of ,bermuda2 but they are also found in ,sicily1 some parts of ,africa and ,america4 ,they are usually mounted in balsam1 but are equally beautiful mounted 8dry0 and used with the lieberkuhn4 ,they require as much care in cleaning as the ,diatomace1 but the process is a different one4 ,sometimes this is effected by simply washing until they are freed from all extraneous matter1 but this is seldom as effectual as it should be4 ,in the ,microscopic ,journal ,mr4 ,furlong gives the following method of treatment as the best he knew3-- ,procure-- ,a large glass vessel with #c or #d quarts of water4 ,new tin saucepan holding #a pint4 #b thin precipitating glasses holding #aj oz4 each4 ,take #c oz4 of dry 8,barbadoes earth0 7lumps are best71 and break into rather small fragments4 ,put #c or #d oz4 of common washing soda into the tin and half fill it with water4 ,boil strongly1 and having thrown in the earth1 boil it for half an hour4 ,pour nine-tenths of this into the large glass vessel1 and gently crush the remaining lumps with a soft bristle brush4 ,add soda and water as before1 and boil again2 then pour off the liquid into the large vessel1 and repeat until nothing of value remains4 ,stir the large vessel with an ivory spatula1 let it stand for three minutes1 and pour gently off nine-tenths of the contents1 when the shells will be left1 partially freed only1 like sand4 #b,,nd ,,process4--,put common washing soda and water into the tin as before1 and having placed the shells therein1 boil for an hour4 ,transfer to the large vessel as before1 and after allowing it to stand for one minute pour off4 ,each washing brings off a kind of 8flock10 which seems to be skins4 #c,,rd ,,process4--,put the shells in precipitating glass and drain off the water until not more than oz4 remains4 ,add half a teaspoonful of bicarbonate of soda1 dissolve1 and then pour in gently #a oz4 of strong sulphuric acid4 ,this liberates the 8flock10 c41 and leaves the shells beautifully transparent4 ,wash well now with water to get rid of all salts and other soluble matter4 ,some of the large shells are destroyed by this method1 but none that are fit for microscopic use4 ,an oblique light shows these objects best4 ,these are sometimes treated in the manner described in ,chapter ,,ii4 where the diatoms are spoken of1 but many forms are liable to be injured by this severe process4 ,it has been before stated that some of the zoophytes may be mounted dry1 and others examined as opaque or transparent objects according to their substance4 ,they are very interesting when examined in the trough whilst living1 but to preserve many of them for future examination they must be mounted in some preservative medium4 ,sometimes this may be one of the liquids mentioned in ,chapter ,,iv41 but if possible they should be kept in balsam1 as there is less danger of injury by accident to this kind of slide4 ,this method of mounting presents some difficulties1 but ,i think that all agree as to the trustworthiness of ,dr4 ,golding ,bird's information on the subject1 which appeared in the ,microscopic ,journal4 ,of this1 space forbids me to give more than a condensed account1 but ,i hope to omit nothing of moment to the reader for whom these pages are written4 ,after stating that there are few who are not familiar with these exquisite forms1 and have not regretted the great loss of beauty they sustain in dying1 he informs us that from their so obstinately retaining air in the cells and tubes when dried1 it is hardly practicable to get rid of it2 and they also shrivel up very seriously in the process of drying4 ,the following plan1 however1 he has found almost faultless in their preparation4 ,to preserve them with extended tentacles1 they should be plunged in cold fresh water1 which kills them so quickly that these are not often retracted4 ,the specimens should be preserved in spirit until there is leisure to prepare them2 if1 however1 they have been dried1 they should be soaked in cold water for a day or two before being submitted to the following processes3-- #a4 ,after selecting perfect specimens of suitable size1 immerse them in water heated to about #abj and place them under the receiver of an air-pump4 ,slowly exhaust the air1 when bubbles will rise and the water appear to be in a state of active ebullition4 ,after a few minutes re-admit the air and again exhaust1 repeating the process three or four times4 ,this will displace the air from most1 if not all1 of the class4 #b4 ,remove the specimens and allow them to drain upon blotting-paper for a few seconds2 then place them in an earthen vessel fitted with a cover1 and previously heated to about #bjj4 ,this heat may be easily got by placing the vessel for a short time in boiling water1 wiping it immediately before use with a thick cloth4 ,the specimens are then dropped into this1 covered with the lid1 and immediately placed under the receiver of the air-pump1 and the air rapidly exhausted4 ,by this means they are dried completely1 and so quickly that the cells have no time to wrinkle4 #c4 ,in an hour or two remove them from the air-pump and drop them into a vessel of perfectly transparent camphine4 ,this may be quite cold when the horny1 tubular polypidoms1 as those of the ,sertulari1 are used2 but should be previously heated to #ajj when the calcareous1 cellular ,polyzoa are the objects to be preserved4 ,the vessel should be covered with a watch-glass and placed under the receiver1 the air being exhausted and re-admitted two or three times4 #d4 ,the slide which is to receive the specimen should be well cleaned and warmed so as to allow the balsam to flow freely over it4 ,this must be applied in good quantity1 and air-bubbles removed with the needle-point4 ,take the polypidom from the camphine1 drain it a little1 and with the forceps immerse it fully in the balsam4 ,the glass to be laid upon it should be warmed and its surface covered with a thin layer of balsam1 and then lowered gradually upon it1 when no bubbles should be imprisoned4 ,a narrow piece of card-board at each end of the object for the cover to rest upon1 prevents any danger of crushing the specimen4 ,this mode of mounting polypidoms1 c41 seems to give almost the complete beauty of the fresh specimens4 ,they are very beautiful objects when viewed with common light1 but much more so when the polarizer is used 7in the manner described a little farther on74 ,to the above instructions there can be little to add2 but ,i may here mention that some young students may not be possessed of the air-pump1 and on this account put aside all search for those specimens which need little looking for at the seaside4 ,many of these1 however1 though they lose some beauty by the ordinary mode of drying1 will by steeping for some time in turpentine not only be freed from the air-bubbles1 but suffer so little contraction that they are a worthy addition to the cabinet4 ,another class of objects is the spicula met with in sponges1 c4 ,these are often glass-like in appearance and of various shapes2 many are found resembling needles 7whence their name72 some from the synapta are anchor-like1 whilst others are star-like and of complex and almost indescribable combinations4 ,as some of these are composed of silex and are consequently not injured by the use of nitric acid1 the animal substance may be got rid of by boiling them in it4 ,those1 however1 which are calcareous must be treated with a strong solution of potash instead2 but whichever way is used1 of course they must afterwards be freed from every trace of residue by careful washing4 ,these spicules may be often found amongst the sand which generally accumulates at the bottom of the jars in which sponges are kept by those who deal in them1 and must be picked out with a camel-hair pencil4 ,the specimens obtained by this means will seldom if ever require any cleaning process1 as they are quite free from animal matter1 c4 ,in the former chapter was noticed those insects or parts of them which are usually mounted dry4 ,when they are large and too opaque to admit of the dry treatment1 they must be preserved in ,canada balsam or fluid4 ,the first of these may now be considered4 ,it may be here mentioned1 that with these objects much heat must not be employed1 as it would in some instances give rise to a cloudiness1 and almost invariably injure them4 ,in killing the insect it is necessary not to rub or break any part of it4 ,this may be performed by placing it in a small box half filled with fragments of fresh laurel leaves1 by immersion in turpentine or strong spirit1 as also in solutions of various poisonous salts4 ,after which it may be preserved for sometime in turpentine or other preservative liquid 7,chapter ,,iv47 until required4 ,as an assistance to the student1 ,i believe that ,i can do no better than give him the plan pursued by my friend ,mr4 ,hepworth1 whose specimens are in every way satisfactory2 but when his method is used1 the insects must not have been placed in turpentine for preservation3-- 8,after destroying the insects in chloroform or sulphuric ether 7methylated being cheaper71 wash them thoroughly in a wide-necked bottle1 half-filled1 with two or three waters2 the delicate ones requiring great care4 ,then immerse them in liquid potash 7or ,brandish's solution1 which is stronger than the usual preparation71 and let them remain a longer or shorter time according to their texture4 ,when ready to remove1 put one by one into a small saucer of clear water1 and with a camel-hair pencil in each hand press them flat to the bottom1 holding the head and thorax with the left-hand brush1 and apply pressure with the other from above1 downwards1 giving the brush a rolling motion1 which generally expels the contents of the abdomen from the thorax4 ,a minute roller of pith or cork might be used instead of the brush4 ,in larger objects1 use the end of the finger to flatten them4 ,large objects require more frequent washing1 as it is desirable to remove the potash thoroughly1 or crystals are apt to form after mounting4 ,having placed them on the slides with thin glass covers1 tied down with thread1,c dry and immerse them in rectified spirits of turpentine2 place the vessel under the receiver of an air-pump1 and keep it exhausted until the turpentine has taken the place of the air-bubbles3 they are then ready for the application of the balsam4 ,larger objects may often with advantage be transferred to a clean slide1 as during the drying there is considerable contraction1 and an outline often remains beyond the margin showing this4 ,when closely corked they may remain in the spirits two or three months4 ,as you take them from the bottle1 wipe as much turpentine off as possible before removing the thread1 and when untied carefully wipe again1 placing the finger on one end of the cover whilst you wipe the other1 and vice vers4 ,by this means you remove as much turpentine from under the cover as is necessary2 then drop the balsam1 thinned with chloroform 7see ,chapter ,i471 upon the slide1 letting the fluid touch the cover1 when it will be taken in between the surfaces by capillary attraction2 and after pressing the cover down it may be left to dry1 or you may hold the slide over a spirit-lamp for a few seconds before pressing down the cover4 ,if heat is not applied1 they are much longer in drying but are more transparent4 ,if made too hot the boiling disarranges the objects1 and if carried too far will leave only the resin of the balsam1 rendering it so brittle that the cover is apt to fly off by a fall or any jar producing sufficient percussion4 ,never lift the cover up1 if possible1 during the operation1 as there is danger of admitting air4 ,a few bubbles may appear immediately after mounting1 but generally subside after a few hours1 being only the chloroform or turpentine in a state of vapour1 which becomes condensed40 ,c ,this applies to the more delicate ones1 which will not bear transferring after being once spread out and dried4 ,this method of preparing and mounting insects ,i can strongly recommend as giving first-rate results2 but where the specimens are small they seldom need the soaking in caustic potash which larger ones must have4 ,it is only necessary to leave them awhile in turpentine1 especially when they have been first dried with gentle pressure between two glasses1 and then mount with balsam in the ordinary way4 ,amongst the insect tribes there is abundant employment1 especially for the lower powers of the microscope4 ,but if the deeper wonders and beauties of the animal economy are to be sought out and studied1 it is desirable that the various parts should be set separately1 in order that they may receive a more undivided attention1 as well as to render them capable of being dealt with under the higher powers4 ,we will1 therefore1 briefly consider the treatment which the different portions require4 ,the eyes of the butterflies1 and indeed of almost all insects1 afford materials for a study which is complete in itself4 ,when examined with a tolerably high power1 instead of finding each eye with an unbroken spherical surface1 it is seen that many are composed of thousands of hexagonal divisions1 each being the outer surface of a separate portion termed the ocellus4 ,in others these divisions are square2 but in all there is a layer of dark pigment surrounding their lower parts4 ,the ocelli may be partly removed from the eye1 which will show how their tapering forms are arranged4 ,but here we have to consider how to place them in balsam for preservation4 ,the eye being removed from the insect1 and the dark pigment removed by the use of a camel-hair pencil1 must be allowed to remain in turpentine at least for some days4 ,the turpentine should then be renewed and the eye well washed in it just before it is to be mounted4 ,it may then be set in balsam in the same way as any other object2--but here a difficulty is met with4 ,the eye being spherical upon the surface required1 must necessarily be 8folded0 or broken in attempting to flatten it4 ,this difficulty may be often overcome by cutting a number of slits round the edges2 but some object to this mode of treatment1 and where it is practicable it is much more satisfactory to mount one in the natural rounded form and another flat4 ,instead1 however1 of mounting the organ whole1 four or five slides may be procured from each of the larger ones1 as those of the dragon-fly1 c4 ,the antenn also are often mounted on separate slides1 as being better suited for higher powers and more minute examination than when connected with the insect4 ,these two projecting organs1 issuing from the head1 are jointed1 and moveable at will4 ,they differ very much in form amongst the various species1 and are well worth the attention of the microscopist4 ,they are usually mounted with the head attached1 and perhaps they are more interesting when thus seen4 ,some few are very opaque1 to prepare which the following method has been advised3-- ,bleach the antenn by soaking in the following solution for a day or two3-- ,hydrochloric acid1 #aj drops4 ,chlorate of potash1 drachm4 ,water1 #a oz4 ,this will render them transparent4 ,wash well1 dry1 and mount in ,canada balsam4 ,instead of the above1 a weak solution of chloride of lime may be used1 by which means the nerves will be well shown4 ,many1 however1 are rendered transparent enough by simply soaking in turpentine for a longer or shorter time4 ,where the antenn1 however1 are 8plumose10 or feather-like1 extreme care is required in mounting1 though the difficulty is not so great as some seem to think4 ,if they are first dried with gentle pressure1 and then subjected to the action of the air-pump in a small quantity of turpentine until the air is thoroughly expelled1 they can be easily finished upon the slide1 especially when balsam and chloroform are used4 ,insects supply us with another series of beautiful objects1 viz41 the feet4,d ,these are sometimes simply dried and mounted without any medium1 as before mentioned2 but most of them are rendered much more fit for examination by using balsam in their preservation1 as it greatly increases their transparency4 ,the smaller kinds may be dried with gentle pressure betwixt blotting-paper1 and then immersed for some days in turpentine1 without requiring the treatment with liquor potass4 ,this immersion will render them beautifully transparent1 when they may be mounted in balsam in the usual manner4 ,d ,see ,mr4 ,hepworth's interesting articles on the fly's foot in the second and third volumes of the ,microscopic ,journal4 ,it is1 however1 sometimes found difficult to fix the feet when expanded1 in which state the interest of the object is greatly increased4 ,mr4 ,ralph recommends the following mode3--8,first wash the feet1 while the insect is yet alive1 with spirits of wine2 then holding it by a pair of forceps close to the edge of a clean piece of glass1 the insect will lay hold of the upper surface by its foot1 then suddenly drop another small piece of glass over it1 so as to retain the foot expanded1 and cut it off with a pair of scissors1 tie up and soak to get rid of air40 ,mr4 ,hepworth says that he never found any difficulty in expanding the foot on a drop of water or well-wetted slide1 and laying a thin glass cover over it1 tying with thread1 drying1 and immersing in turpentine4 ,the mouth1 also1 with its organs1 is an interesting object in many insects4 ,that of the common fly is often made use of1 and is comparatively easy to prepare4 ,by pressing the head1 the tongue 7as it is commonly termed7 will be forced to protrude1 when it must be secured by the same means as the foot1 and may be subjected to the soaking in turpentine1 and mounted as usual4 ,the honey-bee is1 however1 very different in formation1 and is well worth another slide2 indeed1 even in insects of the same class1 the differences are many and interesting4 ,another worthy object of study is the respiration of insects1 which is effected by trache or hollow tubes1 which generally run through the body in one or more large trunks1 branching out on every side4 ,these terminate at the surface in openings1 which are termed spiracles1 or breathing organs4 ,the trache often present the appearance of tubes constructed by a twisted thread1 somewhat resembling the spiral fibres of some plants4 ,these are very beautiful objects1 and are generally mounted in balsam1 for which reason they are mentioned here2 but as they evidently belong to the 8dissecting portion10 they will be fully treated of in another place4 ,amongst the parasitic insects a great variety of microscopic subjects will be found4 ,as these are usually small1 they may be killed by immersion in spirits of turpentine2 and if at all opaque1 may be allowed to remain in the liquid until transparent enough1 and then mounted in ,canada balsam4 ,the acarida1 or mites and ticks1 are well known2 none1 perhaps1 better than those which are so often found upon cheese4 ,flour1 sugar1 figs1 and other eatables1 are much infested by them2 whilst the diseases called the itch in man1 and the mange in animals1 are produced by creatures belonging to this tribe4 ,these animals are sometimes mounted by simply steeping them in turpentine1 and proceeding as with other insects4 ,the 8,micrographic ,dictionary0 gives the following directions as to mounting parts of these3--8,the parts of the mouth and the legs1 upon which the characters are usually founded1 may be best made out by crushing the animals upon a slide with a thin glass cover1 and washing away the exuding substance with water2 sometimes hot solution of potash is requisite1 with the subsequent addition of acetic acid1 and further washing4 ,when afterwards dried and immersed in ,canada balsam1 the various parts become beautifully distinct1 and may be permanently preserved40 ,feathers of different kinds of birds are usually mounted in balsam when required to show much of the structure4 ,this is particularly interesting when the feathers are small1 as they then show the inner substance1 or pith1 as it may be termed1 with the cells1 c4 ,the 8pinn10 or soft branches of the feathers1 will be found of various constructions2 some possessing hooks along one side1 whereby they fasten themselves to their neighbours2 others branching out1 with straight points somewhat resembling the hairs from certain caterpillars4 ,but1 of course1 when the metallic-looking gorgeous colours are all that is required to be shown1 and reflected light used 7as with the feathers of the hummingbird1 peacock1 c471 it is much better that they should be mounted dry1 as in ,chapter ,,ii4 ,the seeds and pollen of plants are most frequently mounted dry1 as mentioned in ,chapter ,,ii42 but the more transparent of the former1 and the darker kinds of the latter1 are perhaps better seen in ,canada balsam4 ,there is nothing particular to be observed in the manipulation1 except that the glass cover must be applied lightly1 otherwise the grains may be crushed4 ,there are some objects which cannot be shown in a perfect manner when mounted dry1 but when immersed in balsam become so very transparent that they are almost useless4 ,to avoid this1 it has been recommended to stain the objects any colour that may be convenient1 and afterwards mount in balsam in the ordinary manner4 ,most objects intended for the polariscope may be mounted in ,canada balsam2 but there are some exceptions to this4 ,many of the salts are soluble in this medium1 or their forms so injured by it1 that glycerine or oil has to be used 7see ,chapter ,,iv472 others must be left in the dry form1 as before mentioned2 and some few it is impossible to preserve unchanged for any length of time4 ,crystals1 however1 are amongst the most beautiful and interesting subjects for polarisation2 and it is very probable that1 by the aid of the polariscope1 new and valuable facts are yet to be made known4 ,for one who finds pleasure in form and colour1 there is a field here which will only open wider upon him as he advances2 and instead of being in anywise a merely mechanical occupation1 it requires deep and careful study4 ,the little here said on the subject will show this in some degree4 ,with almost every salt the method of crystallization must be modified to obtain the best forms2 ,i may even go further than this1 and say that it is possible to change these forms to such a degree that the eye can perceive no relationship to exist betwixt them4 ,if a solution of sulphate of iron is made1 a small quantity spread evenly upon a slide1 and then suffered to dry whilst in a flat position1 the crystals often resemble the fronds of the common fern in shape4 ,but if1 whilst the liquid is evaporating1 it is kept in motion by stirring with a thin glass rod1 the crystals form separately1 each rhombic prism having its angles well defined1 and giving beautiful colours with the polarized light4 ,again1 pyro-gallic acid1 when allowed to flow evenly over the slide in a saturated solution1 covers the surface in long 8needles10 which are richly coloured by polarized light2 but if any small portion of dust or other matter should form a nucleus around which these 8needles0 may gather1 the beauty is wonderfully increased4 ,a form very closely resembling the 8eye0 of the peacock's tail1 both in form and colour1 is then produced1 which to one uninitiated in crystallography bears very little resemblance to the original crystal4 ,from these simple facts it will be clearly seen that in this1 as in every other department1 study and experience are needful to give the best results4 ,to obtain anything like uniformity in the formation of crystals upon the glass slide1 every trace of grease must be removed by cleaning with liquor potass or ammonia immediately before using1 care also being taken that none of the agent is left upon the slide1 otherwise it may interrupt and change their relative position1 and even their form4 ,amongst those which are generally esteemed1 the most beautiful are the crystals of oxalurate of ammonia4 ,the preparation of this salt from uric acid and ammonia is a rather difficult process1 and will not on that account be described here2 but when possessed1 a small quantity of a strong solution in water must be made1 and a little placed on the slide1 and evaporated slowly4 ,part of the salt will then be deposited in circles with the needle-like crystals extending from common centres4 ,they should then be mounted in pure ,canada balsam2 and1 when the best colours are wanted1 used with the selenite plate4 ,of this class of crystal salicine is a universal favourite1 and can be easily procured of most chemists4 ,the crystals may be produced in two ways3--,a small portion of the salt must be placed upon the slide1 and a strong heat applied underneath until fusion ensues2 the matter should then be evenly and thinly spread over the surface4 ,in a short time the crystals will form1 and are generally larger than those procured by the following process2 but the uncertainty is increased a little when fusion is used1 which1 however1 is desirable with many salts4 ,secondly1 make a saturated solution of salicine1 which in cold water is effected by adding one part of the salt to eighteen parts of water4 ,lay a little upon the slide1 and allow it to evaporate spontaneously1 or with the aid of gentle heat4 ,the crystals are generally uniform1 and with ordinary powers quite large enough to afford a beautiful object4 ,the circular shape and gorgeous colours of this crystal have made it so great a favourite that there are few cabinets without it4 ,many new forms may be procured by uniting two totally different salts in solution in certain proportions4 ,this is a field affording new facts and beauties2 but requires some chemical knowledge and much perseverance to obtain very valuable results4 ,one of the most beautiful ,i have met with has been composed of sulphate of copper and sulphate of magnesia4 ,the flower-like forms and uniformity of crystallization when successful make it well worth a few failures at first2 and as ,i became acquainted with some new facts in my frequent trials1 ,i will give the preparation of the double salt from the beginning4 ,make a saturated solution of the two sulphates1 combined in the proportion of three parts copper to one part magnesia1 and then add to the solution one-tenth of pure water4 ,dust or other impurities should be guarded against1 and the slide made free from all trace of grease by cleaning immediately before use with liquor potass or ammonia4 ,a drop of the solution should then be placed upon the slide1 and by a thin glass rod spread evenly upon the surface4 ,heat this whilst in a horizontal position until the salt remains as a viscous transparent substance1 which will not be effected until it is raised to a high degree4 ,the slide may now be allowed to cool1 and when this is accomplished1 the flower-like crystals will be perceived forming here and there upon the plate4 ,when these are at any stage in which it is wished to preserve them1 a few seconds' exposure to the fire1 as warm as the hand can comfortably bear1 will stop the expansion1 when the portion which we wish to mount should be cut off from the mass of salt by simply scratching the film around1 and pure ,canada balsam with the thin glass used4 ,breathing upon the film1 or allowing the slide to become cold and attract the moisture from the atmosphere1 will cause the crystallization to extend1 and sometimes greatly rob the effect2 so it is necessary to mount quickly when the desired forms are obtained4 ,as the crystals are very uncertain as to the place of their formation1 ,i may here mention that they may be got in any part of the slide by piercing the film with a needle-point2 but in some degree this necessarily interferes with the centre4 ,as the cause of this has no need to be entered into here1 and has been elsewhere discussed1 ,i shall only give the above directions1 and say that there is a great field in this branch of study which the microscope alone has opened4 ,it would be useless to enter into particulars respecting the various salts and treatment they require1 as a great difference is effected even by the strength of the solution4 ,there are some crystals1 also1 which are called forth in insulated portions1 showing no formation upon the ground2 but even when mounted in any preserving fluid1 and unchanged for a year1 a new action seems to arise1 and a groundwork is produced which bears little resemblance to the original crystal4 ,sometimes this new formation adds to the beauty of the slide2 in other cases the reverse is the result1 the slide being rendered almost worthless4 ,this action1 ,i believe1 frequently arises from some liquid being contained in the balsam or other mounting medium used2 and this is rendered the more probable by the crystallization being called forth in an hour after the balsam diluted with chloroform is employed1 whereas no change would have taken place for months 7if at all7 had pure balsam been used4 ,sections of some of the salts are very interesting objects1 but the method of procuring these and their nature will be described in ,chapter ,v4 ,the scales of various fish have been before mentioned as mounted 8dry20 when1 however1 they are required for polarising objects they are generally mounted in balsam1 and some few in liquid4 ,the former method will be considered here4 ,the eel affords a beautiful object for this purpose4 ,the scales are covered by a thin 8skin10 which may be slightly raised with a knife and then torn off1 in the same manner as the covering of the geranium and other petals1 described in ,chapter ,,ii4 ,the required portion may then be removed2 or if a piece of skin can be procured as stripped off in cooking1 the scales may be easily taken from the inner surface4 ,they must then be washed and thoroughly cleaned4 ,after drying1 soak for a day in turpentine1 and mount in the ordinary manner with balsam4 ,this is a good polarising object2 but the interest1 and ,i think the beauty1 is increased by procuring a piece of eel's skin with the scales in sit1 washing and drying under pressure1 and mounting in balsam as before4 ,the arrangement of the scales produces beautiful 8waves0 of colour1 which are quite soothing to the eye after examining some of the very gorgeous salts1 c4 ,there are many scales of fish which are good subjects for the polariscope when mounted in balsam2 but as they require no particular treatment1 they need no mention by name4 ,among hairs we find some which are beautiful when mounted in balsam and examined by polarized light4 ,some1 when wanted as common objects1 are always used dry1 as before mentioned2 but if they are intended to be shown as polarizing objects1 they must be placed in some medium4 ,the 8,micrographic ,dictionary0 mentions a mode of making an interesting object by plaiting two series of white horse-hairs at an angle1 mounting in balsam1 and using with the polariscope4 ,all hairs1 however1 must be steeped in turpentine for a short time before mounting1 as they will thus be rendered cleaner and more transparent4 ,when this is done1 there is no difficulty in mounting them4 ,many of the 8tongues0 of fresh-water and marine mollusca are deeply interesting and most beautiful objects when examined by polarized light4 ,as these are usually mounted in balsam1 ,i mention them in this place2 but as they must be removed from the animals by dissection1 particulars respecting them will not be entered into until we come to the part in which that operation is described 7,chapter ,v474 ,the manner of preparing and mounting many of the ,polyzoa and ,zoophytes has been before described2 but any notice of polarizing objects would be incomplete without some allusion to them4 ,a small piece of the ,flustra avicularis1 well prepared1 is beautiful when examined in this manner4 ,no selenite is needed1 and yet the colours are truly gorgeous4 ,it is often met with upon shells and zoophytes of a large size1 and will well repay the trouble of searching for4 ,many of the ,sertularid are very beautiful with polarized light1 and1 indeed1 no ramble upon the seaside need be fruitless in this direction4 ,the different starches are quite a study in themselves1 and are peculiarly connected with polarized light4 ,they are found in the cellular tissue of almost every plant in small white grains which vary considerably in size2 that from the potato averages one-three-hundredth of an inch in diameter1 and that from arrow-root about one-six-hundredth4 ,to procure starch from any plant1 the texture must first be broken up or ground coarsely2 the mass of matter must be then well washed in gently-flowing water1 and1 as all starch is totally insoluble in cold water1 the grains are carried off by the current and deposited where this is stayed4 ,in procuring it from the potato1 as well as many other vegetables1 it is but necessary to reduce the substance to a coarse pulp by the aid of a culinary 8grater20 the pulp should then be well agitated in water1 and allowed to rest a short time1 when the starch will be found at the bottom1 its lighter colour rendering it easily distinguishable from the pulp4 ,it should1 however1 be washed through two or three waters to render it perfectly clean4 ,these grains have no crystalline structure1 but present a very peculiar appearance when examined with polarized light4 ,each grain shows a dark cross whose lines meet at the point where it was attached to the plant1 called the hilum4 ,round the grain1 also1 a series of lines are seen1 as though it were put together in plates4 ,this is more distinctly visible in some kinds than others4 ,as to the mounting of these starches there is little to be said4 ,if the grains are laid upon the slide1 and as small a portion as possible of the balsam diluted with turpentine1 as before mentioned1 be applied1 they will cling to the glass and allow the pure balsam to flow readily over them without being so liable to imprison air-bubbles when the thin glass is put upon them4 ,the raphides1 which were fully described in ,chapter ,,ii41 when required for use with polarized light1 must be mounted in balsam1 and many are found which give beautiful colours4 ,they require no peculiar treatment1 but must be washed quite clean before putting up4 ,there is one class of objects for the polariscope which differs in preparation from any we have yet considered1 and affords very beautiful specimens4 ,some of the plants1 including many of the grasses and the ,equisetace 7i4 e4 horsetails71 contain so large a quantity of silica1 that when the vegetable and other perishable parts are removed1 a skeleton of wonderful perfection remains4 ,this skeleton must be mounted in balsam1 the method of performing which will now be considered4 ,sometimes the cuticle of the equisetum is removed from the plant1 others dry the stem under pressure1 whilst the grasses1 of course1 require no preparation4 ,the vegetable should be immersed in strong nitric acid and boiled for a short time2 an effervescence will go on as the alkalies are being removed1 and when this has ceased more acid should be added4 ,at this point the modes of treatment differ2 some remove the object from the acid and wash1 and having dried1 burn it upon thin glass until all appears white1 when it must be carefully mounted in balsam4 ,i think1 however1 it is better to leave it in strong acid until all the substance1 except the required portion1 is removed2 but this will take a length of time1 varying according to the mass1 c41 of the plant4 ,of course1 when this latter method is used1 the skeleton must be washed from the acid1 c41 before being mounted in balsam4 ,these siliceous cuticles are readily found4 ,the straws of most of the cereals1 wheat1 oat1 c42 the husks1 also1 of some of these2 many canes2 the equisetum1 as before described2 and some of the grasses4 ,many of these are everywhere procurable1 so that the student can never want material for a splendid object for the polariscope4 ,in ,chapter ,,ii4 the scales 7or hairs7 which are often found upon the leaves of plants were mentioned as beautiful objects when mounted dry2 but some of these when detached from the leaf--which is easily done by gently scraping it1 when dried1 with a knife--present brilliant starlike and other forms1 if mounted in balsam and used with the polariscope4 ,there is a little danger1 when placing the thin glass upon the balsam1 of forcing out the scales in the wave of matter which is always ejected2 this may be overcome by applying to the slide1 previously to placing the objects upon it1 an extremely thin covering of the balsam diluted with turpentine as before mentioned1 and thus giving them every chance of adherence2 or by using the balsam with chloroform1 as before noticed4 ,these scales are much more abundant than was formerly supposed1 and daily new specimens are discovered2 so that the student should always be on the lookout for them in his researches in the vegetable world4 ,most classes of objects1 and the treatment they require when mounting them in balsam1 have now been considered4 ,the next chapter will be devoted to the preservative liquids1 and the best methods of using them4 ,,chapter ,,iv4 ,,preservative ,,liquids1 ,,etc41 ,,particularly ,,where ,,cells ,,are ,,used4 ,there are many objects which would lose all their distinctive peculiarities if allowed to become dry1 especially those belonging to the fresh-water ,alg1 many animal tissues1 and most of the very delicate animal and vegetable substances in which structure is to be shown4 ,these must be preserved by immersion in some fluid2 but it is evident that the fluid must be suited to the kind of matter which it is intended to preserve4 ,as it often requires much study and trouble to obtain microscopic objects of this class1 it is well that their preservation should be rendered as perfect as possible2 and for this reason the ,,cells1 or receptacles of the fluids1 should be so closed that all possibility of escape should be prevented4 ,the accomplishment of this is not so easy a matter as it might appear to the inexperienced4 ,before giving any directions as to the manipulation required in mounting the objects1 we must consider the different liquids and cells which are requisite for their preservation4 ,of the former there are a great number1 of which the principal may be mentioned4 ,,distilled ,,water is strongly recommended by many for ,diatomace and other ,protophytes4 ,it has been1 however1 stated that confervoid growths often disturb the clearness of the liquid1 and on this account various additions are made to it4 ,a lump of camphor is often left in the bottle1 so that the water may dissolve as much as possible4 ,one grain of bay-salt and one of alum are added to each ounce of water2 or a drop or two of creosote shaken up with the ounce of water1 which should be afterwards filtered4 ,these additions are often made2 perhaps each of them good for certain objects4 ,,glycerine4--,some affirm this to be one of the best preservative liquids1 especially for vegetable objects2 but others think that it is much better when diluted with two parts of camphor-water1 prepared as above4,e ,e ,dr4 ,carpenter says3--8,glycerine has a solvent power for carbonate of lime1 and should not be employed when the object contains any calcareous structure4 ,in ignorance of this fact1 the author 7,dr4 ,c47 employed glycerine to preserve a number of remarkably fine specimens of the pentacrinoid larva of the ,comatula1 whose colours he was anxious to retain2 and was extremely vexed to find1 when about to mount them1 that their calcareous skeletons had so entirely disappeared1 that the specimens were completely ruined40 ,,glycerine ,,and ,,gum4--,this is also believed to be a very good liquid for vegetable tissues1 and is thus prepared3-- ,pure gum-arabic #a oz4 ,glycerine #a 0 ,water 7distilled7 #a 0 ,arsenious acid #a grains4 ,dissolve the arsenious acid in the cold water1 then the gum1 add the glycerine1 and mix without bubbles4 ,,deane',s ,,compound4--,this is usually deemed about the best medium for preserving ,alg1 mosses1 c41 and is thus prepared3--,soak #a oz4 of best gelatine in #d oz4 of water until the gelatine becomes soft1 when #e oz4 of honey heated to boiling-point are added2 boil the mixture1 and when it has cooled1 but not enough to become stiff1 add oz4 rectified spirit with which #e or #f drops of creosote have been well mixed1 and filter the whole through fine flannel4 ,this compound when cold forms a stiff jelly1 the use of which will be described elsewhere4 ,,glycerine ,,jelly4--,this mixture closely resembles the above1 but as the composition differs a little it may be mentioned here4 ,it is strongly recommended by ,mr4 ,lawrance in the ,microscopic ,journal1 where he states 8that the beautiful green of some mosses mounted two years ago1 is still as fresh as the day they were gathered20 and that this is the only medium he knows which will preserve the natural colour of vegetable substances4 ,he takes a quantity of ,nelson's gelatine1 soaks it for two or three hours in cold water1 pours off the superfluous water1 and heats the soaked gelatine until melted4 ,to each fluid ounce of the gelatine1 whilst it is fluid but cool1 he adds a fluid drachm of the white of an egg4 ,he then boils this until the albumen coagulates and the gelatine is quite clear1 when it is to be filtered through fine flannel1 and to each ounce of the clarified solution add #f drachms of a mixture composed one part of glycerine to two parts of camphor-water4 ,,goadby',s ,,fluid4--,this is much used in the preservation of animal objects2 and seldom1 if ever1 acts upon the colours4 ,it is thus prepared--,bay salt1 #d oz42 alum1 #b oz42 corrosive-sublimate1 #d grains4 ,dissolve these in two quarts of boiling water and filter4 ,for delicate preparations some recommend that this mixture be reduced by the addition of an equal quantity of water2 but where there is bone or shell in the object the above acts injuriously upon it1 in which case this fluid may be used3--,bay-salt #h oz41 corrosive sublimate #b grains1 water #a quart4 ,,thwaites' ,,liquid4--,this is recommended for the preservation of ,alg1 c41 as having little or no action on the colour1 and is thus prepared3--,take one part of rectified spirit1 add drops of creosote enough to saturate it2 to this add sixteen parts of distilled water and a little prepared chalk1 and filter4 ,when filtered1 mix with an equal quantity of camphor-water 7as before mentioned71 and strain through fine muslin before using4 ,,chloride ,,of ,,zinc ,,solution4--,in the 8,micrographic ,dictionary0 this is stated to be 8perhaps the best preservative known for animal tissues40 ,persons of great experience1 however1 have given a very different opinion2 but it is certainly very useful in many cases where a small degree of coagulating action is not injurious4 ,it is used of strengths varying according to the softness of the parts to be preserved2 the average being #bj grains of the fused chloride to #a oz4 of distilled water4 ,to keep this liquid a lump of camphor may be left floating in the bottle4 ,i have heard complaints that this mixture becomes turbid with keeping1 but ,i think this must only be the case when some impurity has got into the bottle4 ,,carbolic ,,acid4--,this substance has not been known long enough to warrant any decided opinion upon its merits4 ,a solution of #a part of acid to #bj of water has been recommended on account of its antiseptic properties4 ,,castor ,,oil4--,this is a very useful preservative for crystals and other objects4 ,many salts are quite destroyed when ,canada balsam is used with them2 but very few are acted upon by this oil4 ,to use it1 it must be dropped in a sufficient quantity to cover the crystal or object to be preserved with a thin coating of oil4 ,it may be necessary sometimes to spread it with a needle or other instrument4 ,the thin glass should then be carefully placed upon it1 so that all air may be excluded2 and should any oil be forced out1 owing to the quantity used being too great1 it must be removed with blotting paper4 ,when the edge of the thin glass cover and the surrounding parts of the slide are as clean as possible1 a coating of sealing-wax varnish or liquid glue must be applied and allowed to dry4 ,a second or even a third coating may be required1 but not before the previous cover is quite dry4 ,these varnishes1 however1 are very brittle1 and it is much safer1 as a finish1 to use one of the tougher cements--gold-size1 for instance--which will render it doubly secure4 ,the above are the principal liquids1 c41 used for preserving objects in cells4 ,the different cells may be here mentioned2 and it is recommended that these should always be kept some time before use in order that the cement may become perfectly dry2 and care must be taken that no cement be used on which the preservative liquid employed has any action whatever4 ,,cement ,,cells4--,where the object is not very thick1 this kind of cell is generally used4 ,they are easily made with the turntable before described2 but when the objects to be preserved are very minute1 these cells need not be much deeper than the ordinary circle of cement on the slide4 ,when1 however1 a comparatively great depth is required1 it is sometimes necessary to make the wall of the cell as deep as possible1 then allow it to dry and make another addition4 ,of these cements gold-size is one of the most trustworthy1 and may be readily used for the shallow cells4 ,the asphaltum and india-rubber1 before noticed1 ,i have found very durable when well baked1 and exceedingly pleasant to work with4 ,it may be used of such a thickness as to give space for tolerably large objects4 ,black japan also is much used4 ,many cements1 however1 which are recommended by some writers1 are worse than useless1 owing to the brittleness which renders their durability uncertain1 as sealing-wax varnish1 liquid-glue1 c4 ,the student may feel himself at a loss in choosing the cement which will give him the safest cells1 many of them becoming partially or wholly dry in a year or two1 as stated in another place4 ,i can only give him a few general directions1 and he must then use his own judgment4 ,of course it would be lost labour to employ any cement upon which the preservative liquid has any action whatever4 ,it is also a good rule to avoid those in whose composition there are any particles which do not become a thorough and intimate portion1 as these unreduced fragments will almost certainly1 sooner or later1 prepare a road by which the liquid will escape2 and1 lastly1 whatever cement he uses1 the cells are always better when they have been kept a short time before use1 as already stated4 ,,gutta-,,percha ,,rings have been recommended by some1 as affording every facility for the manufacture of cells for liquids2 but they cannot be recommended1 as1 after a certain length of time1 they become so brittle as to afford no safeguard against ordinary accidents4 ,often the cells must necessarily be of a large size1 and for this reason are made by taking four strips of glass of the thickness and depth required1 and grinding the places where these are to meet with emery1 so as to form a slightly roughened but flat edge4 ,the glass strip must also be ground on the side where it meets the plate1 and each piece cemented with the marine glue mentioned in ,chapter ,i4 in the following manner3--,on that part of the glass to which another piece is to be attached should be laid thin strips of the glue2 both pieces must then be heated upon a small brass table1 with the aid of the spirit-lamp1 until the strips become melted2 the small piece is then to be taken up and placed upon the spot to which it is to be attached1 and so on until the cell is completed4 ,it will be found necessary to spread the glue over the surface required with a needle or some other instrument1 so that an unbroken line may be presented to the wall of the cell1 and no bubbles formed4 ,too great a heat will 8burn0 the marine-glue1 and render it brittle2 care must be therefore taken to avoid this4 ,when shallow cells are required1 those which are made by grinding a concavity in the middle of an ordinary slide will be found very convenient4 ,the concavities are cut both circular and oblong2 and the surface being flat1 the cover is easily fastened upon it4 ,these are now cheap1 and are very safe as to leakage4 ,circular cells with a flat bottom used to be made by drilling a hole through glass of the required thickness1 and fixing this upon an ordinary slide with marine-glue2 but the danger of breakage and the labour were so great that this method is seldom used now1 and1 indeed1 the rings about to be mentioned do away with all necessity of it4 ,,glass ,,rings4--,where any depth is required1 no method of making a cell for liquids is so convenient as the use of glass rings1 which are now easily and cheaply procurable4 ,they are made of almost every size and depth1 and1 except in very extraordinary cases1 the necessity for building cells is completely done away with4 ,these rings have both edges left roughened1 and consequently adhere very well to the slide1 this adherence being generally accomplished by the aid of marine glue1 as before noticed with the glass cells4 ,gold-size has been occasionally used for this purpose2 and the adherence1 even with liquid in the cell1 ,i have always found to be perfect4 ,this method has the advantage of requiring no heat1 but the gold-size must be perfectly dry1 and the ring must have been fixed upon the slide some time before use4 ,canada balsam has also been used for the same purpose1 but cannot be recommended1 as when it is perfectly dry it becomes so brittle as to bear no shock to which the slide may be ordinarily exposed4 ,these are the cells which are mostly used in this branch of microscopic mounting4 ,the mode of using them1 and the different treatment which certain objects require when intended to be preserved in the before-mentioned liquids1 may now be inquired into4 ,i may mention1 however1 that this class of objects is looked upon by many with great mistrust1 owing to the danger there is of bubbles arising in the cells after the mounting has been completed1 even for years4 ,i know some excellent microscopists who exclude all objects in cells and preservative liquids from their cabinets1 because they say that eventually almost all become dry and worthless2 and this is no matter of surprise1 for many of them do really become so4 ,perhaps this is owing to the slides being sold before they could possibly be thoroughly dry4 ,as to the air-bubbles1 ,i shall have something to say presently4 ,we will now suppose the cell employed is made by placing a glass ring upon the slide with marine glue or gold-size1 and is quite dry4 ,around the edge of the cleaned thin glass which is to cover it1 ,i trace with a camel-hair pencil a ring of gold-size1 and also around the edge of the cell to which it is to adhere4 ,dr4 ,carpenter objects to this1 as rendering the later applications of the gold-size liable to 8run in40 ,all danger of this1 however1 is completely done away with by leaving the slide and cover for awhile until the cement becomes partially 8fixed10 but still adhesive enough to perform its function 7,chapter ,,ii474 ,with many slides this is not accomplished in less than twenty-four hours1 even if left two or three days no injury whatever ensues2 but with other kinds an hour is too long to leave the exposed cement1 so that the operator must use his own discretion4 ,the liquid required may be drawn up by the mouth into the pointed tube mentioned in ,chapter ,i41 and then transferred to the cell4 ,in the various books of instruction1 the object is now to be placed in the cell2 this1 however1 ,i think a great mistake1 as another process is absolutely necessary before we advance so far4 ,the cell1 full of liquid1 must be placed under the receiver of an air-pump1 and the air withdrawn4 ,almost immediately it will be perceived that the bottom and sides of the cell are covered with minute bubbles1 which are formed by the air that is held in suspension by the liquid4 ,the slide may now be removed1 and the bubbles may require the aid of a needle or other point to displace them1 so obstinately do they adhere to the surface of the glass4 ,this process may be then repeated1 and one cause1 at least1 of the appearance of bubbles in cells of liquid will be got rid of4 ,the object to be mounted should also be soaked in one or two changes of the preservative liquid employed1 and1 during the soaking1 be placed under the air-pump and exhausted4 ,it may then be transferred to the cell1 which will probably cause the liquid to overflow a little4 ,the cover with the gold size applied to the edge must then be carefully laid upon the cell1 and slightly pressed down1 so that all air-bubbles may be displaced4 ,the two portions of gold-size will now be found to adhere wherever the liquid does not remain1 although the whole ring may have been previously wet4 ,the outer edge of the thin glass and cell must now be perfectly dried1 and a coating of gold-size applied4 ,when this is dry1 the process must be repeated until the cement has body enough to protect the cell from all danger of leakage4 ,when some preservative liquids are used1 a scum is frequently found upon the surface when placed in the cell1 which must be removed immediately before the cover is laid upon it4 ,i believe this method to be perfectly secure against leakage when carefully performed2 and some of my friends have told me that their experience 7some years7 has been equally satisfactory4 ,in using some of the particular kinds of preservative liquids1 it will be found necessary to make slight change in the manipulation4 ,this will be best explained by mentioning a few objects1 and the treatment they require4 ,for the preservation of the ,mosses1 ,alg1 c41 ,deane's compound is much used1 and considered one of the best media4 ,the specimen to be mounted should be immersed in the compound1 which must be kept fluid by the vessel containing it being placed in hot water4 ,in this state the whole should be submitted to the action of the air-pump1 as it is not an easy matter to get rid of the bubbles which form in and around the objects4 ,the cell and slide must be warmed2 and heat will also be necessary to render the gelatine1 c41 fluid enough to flow from the stock-bottle4 ,the cell may then be filled with the compound1 and the specimen immersed in it4 ,a thin glass cover must then be warmed1 or gently breathed upon1 and gradually lowered upon the cell1 taking care1 as with all liquids1 that no bubbles are formed by the operation4 ,the cover may be fixed by the aid of gold-size1 ,japan1 or any of the usual varnishes1 care being taken1 as before1 that all the compound is removed from the parts to which the varnish is intended to adhere4 ,the glycerine jelly of ,mr4 ,lawrance1 before mentioned1 requires almost a similar treatment4 8,the objects to be mounted in this medium should be immersed for some time in a mixture of equal parts of glycerine and dilute alcohol 7six of water to one of alcohol74 ,the bottle of glycerine jelly must be placed in a cup of hot water until liquefied1 when it must be used like ,canada balsam1 except that it requires less heat4 ,a ring of asphaltum varnish round the thin glass cover completes the mounting40 ,the ,infusoria 7see ,chapter ,,iii47 are sometimes preserved in liquid2 but present many difficulties to the student4 ,different kinds require different treatment1 and consequently it is well1 when practicable1 to mount similar objects in two or more liquids4 ,some are best preserved in a strong solution of chloride of calcium1 others in ,thwaites' liquid1 whilst a few keep their colour most perfectly when in glycerine alone4 ,many of them1 however1 are so very transparent that they present but faint objects for ordinary observance4 ,the ,desmidiace require somewhat similar treatment1 and may be mentioned here4 ,the solution of chloride of calcium has been strongly recommended2 but no preservative liquid seems to be without some action upon them4 ,both of the above classes of objects should be mounted in shallow cells1 so as to allow as high a microscopic power as possible to be used with them4 ,many of the ,,zoophytes which are obtained on our sea-coasts are well preserved by mounting in cells1 in the manner before mentioned1 with ,goadby's fluid1 or distilled water with one of the additions noticed amongst the preservative liquids4 ,for examination by polarized light1 however1 they are usually mounted in balsam 7see ,chapter ,,iii471 whilst those in cells present a more natural appearance as to position1 c41 for common study4 ,as to the use of preservative liquids with the ,diatomace there are various opinions4 ,some experienced microscopists say that there is little or no satisfaction in mounting them in this way4 ,dr4 ,carpenter1 however1 explains this difference by his instructions as to what method should be used when certain ends are desired4 ,he says3 8,if they can be obtained quite fresh1 and it be desired that they should exhibit as closely as possible the appearance presented by the living plants1 they should be put up in distilled water within cement-cells2 but if they are not thus mounted within a short time after they have been gathered1 about a sixth part of alcohol should be added to the water4 ,if it be desired to exhibit the stipitate forms in their natural parasitism upon other aquatic plants1 the entire mass may be mounted in ,deane's gelatine in a deeper cell2 and such a preparation is a very beautiful object for the black-ground illumination4 ,if1 on the other hand1 the minute structure of the siliceous envelopes is the feature to be brought into view1 the fresh diatoms must be boiled in nitric or hydrochloric acid0 7which process is fully described in ,chapter ,,ii474 ,it is very convenient to have many of these objects mounted by two or more of the above methods2 and if they are to be studied1 this is indispensable4 ,mr4 ,hepworth once showed me about one hundred slides which he had mounted in various ways1 for no other purpose than the study of the fly's foot4 ,my friend1 ,mr4 ,rylands1 successfully mounts the diatoms in the state in which he finds them1 and gave me the following method as that which he always employs4 ,he says that he has had no failures1 and hitherto has found his specimens unchanged4 ,take a shallow ring cell of asphalt or black varnish 7which must be at least three weeks old71 and on the cell1 whilst revolving1 add a ring of benzole and gold-size mixed in equal proportions4 ,in a minute or two pure distilled water is put in the cell until the surface is slightly convex4 ,the object having been already floated on to the cover 7the vessel used for this purpose being an ordinary indian-ink palette71 is now inverted and laid carefully upon the water in the cell4 ,by these means the object may be laid down without being removed4 ,the superfluous moisture must not be ejected by pressure1 but a wetted camel-hair pencil1 the size made in an ordinary quill1 being partially dried by drawing through the lips1 must be used repeatedly to absorb it1 which the pencil will draw by capillary attraction as it is very slowly turned round4 ,when the cover comes in contact with the benzole and gold-size ring1 there is no longer any fear of the object being removed1 and a slight pressure with the end of the cedar stick of the pencil will render the adhesion complete1 and cement the cover closely and firmly to the cell4 ,when dry1 an outer ring of asphalt makes the mounting neat and complete4 ,the ,fungi have been before mentioned2 but it may be here stated that some few of the minute forms are best preserved in a very shallow cell of liquid4 ,for this purpose creosote-water may be advantageously used4 ,the antenn of insects have been before noticed as being very beautiful when mounted in balsam4 ,this is readily accomplished when they are large2 but those of the most minute insects are much more difficult to deal with1 and are less liable to injury when put up in fluid4 ,goadby's ,fluid serves this purpose very well2 but1 of course1 the object must be thoroughly steeped in the liquid before it is mounted1 for a longer or shorter time according to the thickness4 ,the eggs of insects afford some worthy objects for the microscope1 amongst which may be mentioned those of the common cabbage butterflies 7small and great71 the meadow-brown1 the puss-moth1 the tortoiseshell butterfly1 the bug1 the cow-dung fly1 c4 ,these1 however1 shrivel up on becoming dry1 and must1 therefore1 be preserved in some of the fluids before mentioned4 ,to accomplish this no particular directions are required2 but the soaking in the liquid about to be employed1 c41 must be attended to as with other objects4 ,glycerine may be advantageously used for the preservation of various insects4 ,these should first be cleaned with alcohol to get rid of all extraneous matter1 and then1 after soaking in glycerine1 be mounted with it like other objects4 ,this liquid may also be used for the ,entomostraca1 which offer a wide field for study4 ,they are to be found abundantly in ponds of stagnant water1 c4 ,some insects1 such as ,may-flies1 c41 are1 however1 often preserved by immersion in a solution of one part of chloride of calcium in three or four parts of water2 but this has not been recommended amongst the 8preservative liquids10 as the colour1 which is often an attractive quality of this class of objects1 is thereby destroyed4 ,we have now noticed the treatment which must be applied to those objects which are to be preserved in liquids and cells4 ,we may here state that all slides of this kind should be examined at short intervals1 as they will be found now and then to require another coating of varnish round the edge of the thin glass cover to prevent all danger of leakage4 ,the use of the air-pump1 in the first instance 7as before recommended71 and this precaution as to the varnish1 will render the slides less liable to leakage and air-bubbles1 which so very frequently render them almost worthless4 ,,chapter ,v4 ,,sections ,,and ,,how ,,to ,,cut ,,them1 ,,with ,,some ,,remarks ,,on ,,dissection4 ,many objects are almost worthless to the microscopist until the extraneous matter is removed from them2 and this is frequently difficult in the extreme to perform satisfactorily4 ,as an instance1 certain ,foraminifera may be mentioned in which the cells are placed one upon another1 consequently the object must be reduced to a certain degree of thinness before a single uniform layer of these cells can be obtained to show something of the internal arrangements4 ,most animal and vegetable forms require an examination of the separate parts before much can be known about them4 ,the mass must be divided into separate portions1 each part intended to be preserved being cleaned from the useless matter with which it is surrounded4 ,it will frequently be found necessary to make thin sections1 which from a very tender substance is no easy matter2 and much patience will be necessary to attain anything like proficiency4 ,this making of sections was not until very recently entered into by many except those belonging to the medical profession1 but ,i do not see why this should be so1 as much may be accomplished by a persevering and interested mind where there is time for entering into the subject4 ,i will therefore make an attempt to give some instructions on this subject also4 ,we will first consider the cutting of sections from hard substances1 in which the ordinary knife1 chisel1 c41 are of no avail4 ,most of these require no particular care in mounting1 but are placed in balsam like the other objects noticed in ,chapter ,,iii43 where1 however1 any special treatment is necessary it will be commented upon as we proceed4 ,,shells1 ,c4--,it is seldom1 if ever1 necessary to possess apparatus for this process except a small thin saw made with a steel blade1 for which a piece of watch-spring serves very well2 a fine stone such as is used for sharpening pen-knives2 and two smooth leather strops1 one of which is to be used with putty-powder to polish the section after grinding1 and the other dry1 to give the final surface4 ,it is1 however1 very convenient to have three or four files of different degrees of fineness4 ,the shell1 if very thick1 may be divided by using the watch-spring saw2 and this section may then with ordinary care be rubbed down with water on the stone until one side of it is perfectly flat4 ,when this is accomplished it must be again rubbed with putty-powder upon the strop1 and finally upon the other strop without the powder4 ,this surface will then be finished and must be firmly united to the slide in the position it is intended to occupy4 ,to do this a small quantity of ,canada balsam may be dropped upon the middle of the slide and heated over the lamp until on cooling it becomes hard2 but this must be stopped before it is rendered brittle4 ,upon this the polished surface must be laid1 and sufficient heat applied to allow the object to fall closely upon the slide1 when slight pressure may be used to force aside all bubbles1 c4 ,on cooling1 the adherence will be complete enough to allow the same grinding and polishing upon the upper surface which the lower received4 ,whilst undergoing this1 the section must be examined from time to time to ascertain whether the necessary degree of thinness has been reached4 ,when this is the case the section should be washed thoroughly and dried4 ,it must then be covered1 which is best done by using the ordinary ,canada balsam1 as recommended in ,chapter ,,iii4 ,sections of some exquisitely beautiful objects are cut with much less trouble than the above4 ,the ,orbitolite1 for instance1 may be prepared in this manner4 ,take the object and by pressure with the finger rub the side upon a flat and smooth sharpening stone with water until the portion is reached which it is wished to show4 ,the strength of the object will easily allow this to be accomplished with ordinary care4 ,this side may then be attached to the glass slide with heated balsam1 as above described1 and the object may then be gently rubbed down to the degree of thinness required to show it to the best advantage4 ,after removing all disengaged matter from the object by washing and thoroughly drying1 it may be mounted in balsam in the usual manner1 when it is equally beautiful as a transparent or opaque object4 ,from this it will be seen that in many instances where a smooth stone is found sufficient for the work 7which is often the case when the section is mounted in balsam7 the final process of polishing advised above may be dispensed with1 as in the ,orbitolite1 ,nummulite1 c41 c4 ,it is quite necessary that the stones on which the objects are rubbed be perfectly flat1 otherwise one side must be acted upon before the other1 and it will be found impossible to attain anything like uniformity4 ,where it is not practicable to cut a section and the object is very thick1 a coarse stone may be first used to reduce it and the smoother afterwards4 ,the consideration of the cutting of sections from shells would scarcely be deemed complete without some mention of what ,dr4 ,carpenter terms the decalcifying process4 ,muriatic acid is diluted with twenty times its volume of water1 and in this the shell is immersed4 ,after a period1 differing according to the thickness of the shell1 the carbonate of lime will be dissolved away1 and a peculiar membrane left1 showing the structure of the shell very perfectly4 ,this may be mounted dry1 in balsam1 or sometimes in liquid1 according to the appearance of the object2 but no rule can be given4 ,the discretion of the student1 however1 will enable him to choose the most suitable method4 ,from some shells it is easy to divide thin plates1 or 8lamin10 which require nothing but mounting in ,canada balsam to show the texture very well4 ,in working1 however1 with those which are 8pearly10 it will be found that experience and patience are needed1 as they are very brittle and peculiarly hard2 but a little practice will overcome these difficulties4 ,amongst the ,echinodermata1 which include the star-fishes1 sea-hedgehogs1 c41 there are many whose outer surface is covered with 8spines10 or thin projections4 ,some of these are sharp and thorn-like1 others blunt1 longer or shorter1 and1 indeed1 of endless variety4 ,in many of these1 when a section is made1 rings are seen which have a common centre1 with radiating supports1 resembling sections of some of the woods4 ,these are very beautiful objects1 and methods of procuring them may now be considered4 ,it is the best to cut as thin a section as can safely be got with the watch-spring saw first1 when the smooth 8sharpening stone0 may be used to polish one side1 which is easily accomplished with water only4 ,when this is effected1 it must be washed clean1 and thoroughly dried1 and then may be united to the slide in the same manner as before recommended for the ,orbitolite1 c4 ,if it is ever necessary to displace it on account of inequalities1 bubbles1 or other remediable fault1 this may be done by warming the slide2 though too much heat must be avoided1 otherwise fresh bubbles will certainly be produced4 ,the covering with thin glass1 balsam1 c41 will present no difficulty to the student2 but he must remember that the transparency is somewhat increased by this last operation4 ,corals are often treated in this way1 in order to reveal their structure4 ,except1 however1 the student has had much practice1 he will often find this a most difficult task1 as many of them are exceedingly brittle4 ,he will find the method before described equally applicable here1 and should take both horizontal and vertical sections4 ,,coal4--,this substance is one of the most interesting objects to the microscopist4 ,it is1 of course1 of a vegetable origin2 and though this is in many cases of such minute separate portions as to have lost all appearance of vegetation1 yet it is very frequently met with in masses1 bearing the form1 even to the minute markings1 of wood1 in various directions4 ,to see this and prepare it for microscopic research1 a suitable piece of coal must be obtained2 but in every case the cutting and preparation of these sections require great care and skill4 ,sometimes the coal is first made smooth on one side1 fastened to the glass1 reduced to the requisite degree of thinness1 and finished in the method before described4 ,this mode of treating it is sometimes1 however1 very tantalizing1 as1 at the last moment1 when the section is about thin enough1 it often breaks up1 and so renders the trouble bestowed upon it fruitless4 ,the dark colour and opacity of coal render an extraordinary thinness necessary1 and so increase the liability to this accident4 ,perhaps the best method which can be pursued is that recommended in the 8,micrographic ,dictionary10 which is as follows3--8,the coal is macerated for about a week in a solution of carbonate of potash2 at the end of that time it is possible to cut tolerably thin slices with a razor4 ,these slices are then placed in a watch-glass with strong nitric acid1 covered and gently heated2 they soon turn brownish1 then yellow1 when the process must be arrested by dropping the whole into a saucer of cold water1 else the coal would be dissolved4 ,the slices thus treated appear of a darkish amber colour1 very transparent1 and exhibit the structure1 when existing1 most clearly4 ,we have obtained longitudinal and transverse sections of coniferous wood from various coals in this way4 ,the specimens are best preserved in glycerine in cells2 we find that spirit renders them opaque1 and even ,canada balsam has the same defect4 ,schulz states that he has brought out the cellulose reaction with iodine1 in coal treated with nitric acid and chlorate of potash40 ,cannel-coal is so close and firm in its structure as to be much used instead of jet in the manufacture of ornaments3 it takes a beautiful polish1 and consequently presents the student with none but ordinary difficulties in getting sections of it4 ,its formation is somewhat different from that of coal1 sometimes showing the transition very clearly4 ,in flint there are often found remains of sponges1 shells1 ,diatomace1 c42 but to show these well1 sections must be cut and polished by the lathe and wheel of the lapidary1 which the microscopic student seldom possesses4 ,thin chippings may1 however1 be made1 which when steeped in turpentine and mounted in balsam1 will frequently show these remains very well4 ,teeth are very interesting objects to all microscopists1 more especially to those who give much study to them2 as the class of animal may very frequently be known from one solitary remaining tooth4 ,to examine them thoroughly1 it is necessary to cut sections of them2 but this is rather difficult to perform well1 and needs some experience4 ,some instructions1 however1 will at least lessen these difficulties1 and we will now endeavour to give them4 ,it is generally thought that ,canada balsam injures the finer markings of these sections1 consequently1 they are almost invariably mounted dry4 ,a thin piece is first cut from the tooth with the saw of watch-spring before mentioned1 if possible2 but should the substance be too hard for this1 the wheel and lathe must be used with diamond dust4 ,if this cannot be procured1 there is no alternative but to rub down the whole substance as thin as practicable on some coarse stone or file4 ,the surface will then be rough2 but this may be much reduced by rubbing upon a flat sharpening stone with the finger1 or a small piece of gutta-percha1 upon the object to keep it in contact4 ,the scratches may be much lessened by this1 but not so thoroughly removed as microscopic examination requires in dry sections4 ,it must1 therefore1 be polished with the putty-powder and dry strop1 as recommended in the working of the shell-sections4 ,the other side of the section of the tooth may then be rubbed down to the requisite thinness1 and polished in the same manner1 when the dust and other impurities must be removed by washing1 after which the section must be carefully dried and mounted4 ,some of these sections are equally interesting as opaque or transparent objects4 ,the dentine of the teeth may be decalcified by submersion of the section in dilute muriatic acid2 after drying and mounting in ,canada balsam it presents a new and interesting appearance1 showing the enamel fibres very beautifully when magnified about three hundred diameters4 ,a friend tells me that after submersion of the whole tooth in the acid he has been able to cut sections with a razor4 ,,sections ,,of ,,bone4--,with the aid of the microscope few fragmentary remains have proved so useful to the geologist and students of the fossil kingdom as these4 ,from a single specimen many of our naturalists can tell with certainty to what class of animal it has once belonged4 ,to arrive at this point of knowledge much study is necessary1 and sections of various kinds should be cut in such a manner as will best exhibit the peculiarities of formation4 ,the methods of accomplishing this will now be considered4 ,it may1 however1 be first mentioned that the chippings of some bones will be found useful now and then1 as before stated with flint1 though this is by no means a satisfactory way of proceeding4 ,sometimes the bones may be procured naturally so thin that they may be examined without any cutting2 and only require mounting dry1 or in fluid1 as may be found the best4 ,when commencing operations we must provide the same apparatus as is needed in cutting sections of teeth1 before described4 ,a fine saw1 like those used for cutting brass1 c42 two or three flat files of different degrees of coarseness2 two flat 8sharpening0 stones2 and a leather strop with putty-powder for polishing4 ,as thin a section as possible should first be cut from the part required by the aid of the fine saw2 and it is better when in this state to soak it for some short time in camphine1 ether1 or some other spirit to free it from all grease4 ,with the aid of a file we may now reduce it almost to the necessary degree of thinness1 and proceed as before recommended with teeth4 ,the 8sharpening0 stone will remove all scratches and marks sufficiently to allow it to be examined with the microscope to see if it is ground thin enough2 and if it is to be mounted dry we must polish it with putty-powder and water upon the strop to as high a degree as possible1 and having washed all remains of polishing powder1 c41 from the section we must place it upon the slide and finish it as described in ,chapter ,,ii4 ,if the bone is not sufficiently hard in its nature to bear the above method of handling whilst grinding and polishing--as some are far more brittle than others--as thin a section as possible must first be cut with the saw1 and one surface ground and polished4 ,the piece must then be dried and united to the glass by heated balsam in the same manner as shells1 c4 ,after which the superabundance of balsam must be removed from the glass2 then rub down upon the stone and strop as before4 ,when the polishing is completed the whole slide must be immersed in chloroform1 ether1 or some other spirit1 to release and cleanse the section1 when it may be mounted as the one above mentioned4 ,some have recommended a strong solution of isinglass to affix the half-ground teeth or bones to the glass as causing them to adhere very firmly and requiring no heat1 and also being readily detached when finished4 ,the reason why the sections of bone are usually mounted dry is that the 8lacun10 bone cells1 and canaliculi 7resembling minute canals7 show their forms1 c41 very perfectly in this state1 as they are hollow and contain air1 whereas if they become filled with liquid or balsam--which does sometimes occur--they become almost indistinguishable4 ,there are some dark specimens1 however1 where the cells are already filled with other matter1 and it is well to mount these with balsam and so gain a greater degree of transparency4 ,to gain a true knowledge of the structure of bone1 sections must be cut as in wood1 both transversely and longitudinally2 but with fossil bones1 without the lapidary's wheel1 c41 it is a laborious task1 and indeed can seldom be properly accomplished4 ,in this place1 also1 it may be mentioned that by submitting bone to the action of muriatic acid diluted ten or fifteen times with water1 the lime1 c41 is dissolved away and the cartilage is left1 which may be cut into sections3 in caustic potash the animal matter is got rid of4 ,both of these preparations may be mounted in fluid4 ,the method of cutting thin sections of bone may be also employed with the stones of fruit1 vegetable ivory and such like substances2 many of which show a most interesting arrangement of cells1 especially when the sections are transverse4 ,most of these objects present a different appearance when mounted dry to that which they bear when in balsam1 owing to the cells becoming filled2 and to arrive at a true knowledge of them we must have a specimen mounted in both ways4 ,to those who study polarized light1 few objects are more beautiful than the sections of the different kinds of horn4 ,we will briefly inquire into the best method of cutting these4 ,there are three kinds of horn1 the first of which is hard1 as the stag's1 and must be cut in the same manner as bone4 ,the second is somewhat softer1 as the cow's4 ,the third is another and still softer formation1 as the 8horn0 7as it is termed7 of the rhinoceros4 ,in cutting sections of the two last we should succeed best by using the machine invented for these purposes which ,i shall shortly describe when the method of cutting wood is considered4 ,to aid us in this when the horn is hard it must be boiled for a short time in water1 when the cutting will be more easily accomplished4 ,the sections should be both transverse and longitudinal1 those of the former often showing cells with beautiful crosses1 the colours with the selenite plate being truly splendid4 ,of this class the rhinoceros horn is one of the best2 but the buffalo also affords a very handsome object4 ,the cow's1 and indeed almost every different kind of horn1 well deserves the trouble of mounting4 ,whalebone1 when cut transversely1 strongly resembles those of the third and softer formation4 ,all these are best seen when mounted in ,canada balsam1 but care must be taken that they have been thoroughly dried after cutting1 and then steeped in turpentine4 ,an interesting object may also be procured from whalebone by cutting long sections of the hairs of which it is composed4 ,down the centre of each hair we shall find a line of cells divided from one another very distinctly4 ,and 7as recommended in the 8,micrographic ,dictionary07 if whalebone be macerated twenty-four hours in a solution of caustic potash it will be softened1 and by afterwards digesting in water1 the outer part will be resolved into numerous transparent cells1 which will show more plainly the structure of this curious substance4 ,in a former chapter1 hairs were mentioned1 their many and interesting forms1 and their beauty when used with polarized light4 ,the sections of them1 however1 are no less a matter of study1 as this mode of treatment opens to sight the outer 8casing10 and the inner substance somewhat resembling the pith of plants4 ,it would be out of place to enter into the description of the different forms met with2 but the ways in which sections are to be procured may be glanced at4 ,if transverse sections are required1 some place a quantity of hairs betwixt two flat pieces of cork1 which by pressure hold them firmly enough together to allow the required portions to be cut with a razor4 ,others take a bundle of the hairs and dip it into gum or glue1 which gives it when dry a solidity equal to wood4 ,sections of this are then cut with the machine mentioned a little further on1 and these may be mounted in balsam4 ,the human hair is easily procured in the desired sections by shaving as closely as possible a second time and cleansing from the lather1 c41 by carefully washing4 ,most hairs1 however1 should be examined both transversely and longitudinally4 ,it is not difficult to procure the latter1 as we may generally split them with the aid of a sharp razor4 ,in a great number of hairs there is a quantity of greasy matter which must be got rid of by soaking in ether or some other solvent before mounting4 ,we may next consider the best method of procuring sections of wood1 which must be cut of such a degree of thinness as to form transparent objects1 and so display all the secrets of their structure4 ,there is no monotony in this study1 as the forms are so various1 and the arrangement of the cells and woody fibre so different1 that the microscopist may find endless amusement or study in it4 ,from a single section the class of trees to which it has belonged may be known1 often even when the wood is fossil4 ,the apparatus best adapted for cutting these sections is made as follows3--,a flat piece of hard wood1 about six inches long1 four wide1 and one thick1 is chosen1 to which another of the same size is firmly fixed1 so as to form1 in a side view1 the letter ,t4 ,on one end of the upper surface is fastened a brass plate1 perfectly flat1 in the centre of which a circular opening is cut about half an inch in diameter4 ,coinciding with this opening is a brass tube1 fixed in the under side of the table 7if it may be termed so74 ,this tube is so cut at the bottom as to take a fine screw4 ,another screw is also placed at the same end of the 8table10 which works at right angles to this1 so that any substance in the tube may be wedged firmly by working this last screw4 ,to use this instrument1 the piece of wood or other object of which a section is required must be placed in the tube1 when1 by turning the screw underneath1 the wood is raised above the brass plate more or less as wished1 and by using the screw at the end1 it is held firmly in the same position4 ,with a flat chisel the portion of the object which projects above the surface of the brass plate may now be cut off1 and by means of the bottom screw another portion may be raised and treated in the same manner4 ,as to the thickness of which objects should be cut1 no proper directions can be given1 as this differs so greatly that nothing but experience can be any guide4 ,the same thickness can be obtained by working the screw underneath in uniform degrees1 the head being marked for this purpose2 and when the substance to be cut is very much smaller than the hole in the brass plate1 it may be wedged with cork4 ,as this instrument is peculiarly adapted for cutting wood 7though used for other substances1 as before mentioned71 ,i shall notice a few particulars concerning this branch of sections4 ,it may here be remarked1 that to obtain anything like a true knowledge of the nature of wood1 it should be cut and examined in at least two directions1 across and along4 ,the piece of wood is often placed in spirits for a day or two1 so that all resinous matter may be dissolved out of it2 it must then be soaked in water for the same length of time1 so as to soften and render it easy to cut4 ,sections are obtained in the manner described above1 but often curl to such a degree as to make it necessary to immerse them in water1 from which they may be taken and dried under slight pressure4 ,they are often mounted dry1 and require no care beyond other objects1 as in ,chapter ,,ii4 ,some1 however1 are best mounted in balsam1 particularly the long sections when used for the polariscope2 these must be soaked in turpentine1 and the greatest care taken that all air bubbles are got rid of4 ,others are thought to be most useful when mounted in shallow cells with some of the preservative liquids mentioned in ,chapter ,,iv4--weak spirit and water1 chloride of calcium solution of the strength of one part of the salt to three parts of distilled water1 c4 ,the above 8section-cutter0 may not be within the reach of every student1 nor is it absolutely necessary2 though where any great number of specimens is required it is very useful1 and insures greater uniformity in the thickness4 ,many employ a razor for the purpose1 which must always be kept sharp by frequent stropping4 ,sections of leaves also may be procured by the same means1 though1 as before mentioned1 they are sometimes easily divided by stripping the coatings off with the fingers4 ,the cells which come to sight by cutting some of the orchideous plants are most interesting4 ,to cut these leaves they may be laid upon a flat piece of cork1 thus exposing the razor to no danger of injury by coming in contact with the support4 ,it may be mentioned here that the razor may also be used in cutting sections of the rush1 than which a more beautiful object can scarcely be found when viewed transversely1 as it shows the stellate arrangements of the ducts to convey the liquids to the different parts of the plant very clearly4 ,this should be mounted dry4 ,in the same way sections of the leaf-stalks of ferns may also be cut1 some of which1 as ,dr4 ,carpenter states1 show the curious ducts very beautifully1 especially when cut rather obliquely4 ,when sections of the softer substances are required1 no instrument can be compared with 8,valentin's knife10 which consists of two steel blades lying parallel with one another and attached at the lower end4 ,the distance of separation may be regulated at will by a small screw near the handle4 ,when1 therefore1 a section is wanted1 the substance must be cut through1 and betwixt the blades a thin strip will be found1 which may be made of any thickness1 according to the distance of their separation4 ,by loosening the screw the blades may be extended1 and the section may be floated out in water if the damp will not injure it4 ,the knife cuts much better if dipped in water immediately before use and also when the substance to be operated upon is wet1 or even under water altogether2 but care must be taken1 after use1 to clean the blades thoroughly and oil them before laying by1 if the place is at all damp4 ,this instrument is most useful in such subjects as anatomical preparations where the sections are required to show the position of the different vessels1 c42 but1 as before stated1 is very valuable for all soft substances4 ,as an instance of this1 it may be mentioned1 that it is frequently used in cutting sections of sponges2 but as these are often very full of spicula1 c41 it is much better to press the sponge flat until dry1 and then cut off thin shavings with a very sharp knife2 these shavings will expand when placed in water4 ,after this they may be laid betwixt two flat surfaces and dried1 when they may be mounted as other dry objects1 or1 when desirable1 in balsam4 ,valentin's knife is very much used in taking sections of skin1 which are afterwards treated with potash solution1 acids1 c41 to bring out in the best way the different portions4 ,dr4 ,lister's mode1 however1 of getting these is thus given in the ,microscopic ,journal3--8,but ,i afterwards found that much better sections could be obtained from dried specimens4 ,a portion of shaved scalp being placed between two thin slips of deal1 a piece of string is tied round them so as to exercise a slight degree of compression2 the preparation is now laid aside for twenty-four hours1 when it is found to be dried to an almost horny condition4 ,it then adheres firmly by its lower surface to one of the slips1 and thus it can be held securely1 while extremely thin and equable sections are cut with great facility in any plane that may be desired4 ,these sections1 when moistened with a drop of water and treated with acetic acid1 are as well suited for the investigation of the muscular tissue as if they had not been dried40 ,there are many who almost confine their attention to polarized light and its beautiful effects4 ,such would not deem these efforts to aid the student in cutting sections complete without some notice of those which are taken from various crystals1 in order to display that curious and beautiful phenomenon1 the rings with a cross4 ,the arrangement of these is somewhat changed by the crystal which affords the section2 but nitrate of potash gives two sets of rings with a cross1 the long line of which passes through both1 the short line dividing it in the middle4 ,the process of cutting these sections is rather difficult1 but a little care and perseverance will conquer all this4 ,the following is extracted from the ,encyclopdia ,metropolitana3--8,nitre crystallizes in long six-sided prisms whose section1 perpendicular to their sides1 is the regular hexagon4 ,they are generally very much interrupted in their structure2 but by turning over a considerable quantity of the ordinary saltpetre,f of the shops specimens are readily found which have perfectly transparent portions of some extent4 ,selecting one of these1 cut it with a knife into a plate above a quarter of an inch thick1 directly across the axis of the prism1 and then grind it down on a broad wet file till it is reduced to about one quarter or a sixth of an inch thick1 smooth the surface on a wet piece of emeried glass1 and polish on a piece of silk strained very tight over a strip of plate-glass1 and rubbed with a mixture of tallow and colcothar of vitriol4 ,this operation requires practice4 ,it cannot be effected unless the nitre be applied wet and rubbed till quite dry1 increasing the rapidity of the friction as the moisture evaporates4 ,it must be performed in gloves1 as the vapour from the fingers1 as well as the slightest breath1 dims the polished surface effectually4 ,with these precautions a perfect vitreous polish is easily obtained4 ,we may here remark1 that hardly any two salts can be polished by the same process4 ,thus1 ,rochelle-salt must be finished wet on the silk1 and instantly transferred to soft bibulous linen and rapidly rubbed dry4 ,experience alone can teach these peculiarities1 and it is necessary to resort to contrivances 7sometimes very strange ones7 for the purpose of obtaining good polished sections of soft crystals1 especially of those easily soluble in water4 8,the nitre is thus polished on both its surfaces1 which should be brought as near as possible to parallelism40 ,f ,sometimes the saltpetre of the shops is nitrate of soda1 and as this is slightly deliquescent1 it is well to be certain that we have the nitrate of potash1 which is free from this defect4 ,some sections of the naturally formed crystals also show the 8rings0 very well1--as ,iceland ,spar1 which gives a single ring and cross2 but the difficulty of cutting and polishing them is almost too great for the amateur1 and must be left to the lapidary4 ,this curious phenomenon1 however1 may be seen by using a plate of ice uninterruptedly formed of about one inch in thickness4 ,before concluding these remarks on sections1 ,i must mention a few difficulties which may be met with1 and their remedies4 ,the foremost of these is the softness of some objects1 which have not resistance enough in themselves to bear cutting even with the sharpest instruments4 ,this may often be removed by soaking in a solution of gum1 and then drying1 which will render the substance firm enough to be cut1 when the sections must be steeped in water1 and the gum thus got rid of4 ,small seeds1 c41 may be placed in wax when warmed1 and will be held firmly enough when it is again cold to allow of them being cut into sections1 c4 ,and1 lastly1 where a substitute for a microscopist's hand-vice is required1 a cork which fits any tube large enough may be taken and split1 the object being then placed between the two parts1 and the cork thrust into the tube1 a sufficient degree of firmness will be obtained to resist any necessary cutting1 c4 ,,dissection4--,as ,i stated at the commencement of this chapter1 no written instructions can enable any student to become an adept in this branch without much experience and no little study4 ,i will1 however1 describe the necessary apparatus1 and afterwards mention the mode of treatment which certain objects require4 ,a different microscope is manufactured for the purpose of dissection1 most first-rate makers having their own model4 ,the object-glasses of many of these are simple1 and consequently not expensive2 but one of the great requisites is a stage large enough to hold the trough1 in which the operation is often performed4 ,where this is the case it would scarcely be worth the expense of getting a dissecting microscope if the student were pursuing no particular study1 but merely made use of the instrument when an object to be operated upon turned up accidentally4 ,the ordinary form is much improved for this purpose1 by having two wooden rests placed at the sides of the microscope1 upon which the hands may be supported when working upon the stage4 ,these should be weighty enough to be free from danger of moving4 ,these supports will also be found to be a remedy against much of the weariness which inevitably arises from having to sustain the hands as well as work with them4 ,the erector1 as ,i before observed1 is necessary to a young student2 but with a little practice he may work very well without it4 ,we will now notice some of the instruments which are most useful in dissection4 ,two or three different sizes of ordinary scissors should be possessed1 but the shapes must be modified in others for many purposes1 as those used by surgeons2 a pair with the cutting parts bent in a horizontal direction1 and another pair slightly curved in a perpendicular2 so that parts of the substance operated upon may be reached1 which it would be impossible to touch with straight scissors4 ,one point of these is sometimes blunt1 and the other acute1 being thus made very useful in opening tubular formations4 ,another form of these is made1 where the blades of the scissors are kept open by a spring1 the handles being pressed together by the fingers4 ,where it is desirable1 one or both of these handles may be lengthened to any degree by the addition of small pieces of wood4 ,,the ,,knives which are most useful are those of the smallest kind which surgeons employ in very delicate operations4 ,these are made about the length of an ordinary pen-knife1 and are fixed in rather long flattish handles2 some are curved inwards1 like the blade of a scythe1 others backwards2 some taper to a point1 whilst others again are broad and very much rounded4 ,complete boxes are now fitted up by the cutlers1 of excellent quality and surprisingly cheap4 ,,needles4--,these are very useful and should be firmly fixed in handles as recommended in ,chapter ,i4 ,it is convenient to have them of various lengths and thicknesses4 ,if curved by heating and bending to any required shape they may be re-hardened by putting them whilst hot into cold water4 ,dr4 ,carpenter also makes edged instruments by rubbing down needles upon a hone4 ,they are more pleasant to work with when short1 as the spring they have whilst long robs them of much of their firmness4 ,a glass syringe is also useful in many operations1 serving not only to cleanse the objects but to add or withdraw liquids from the dissecting-trough4 ,this trough will now be described1 as many substances are so changed by becoming dry that it is impossible to dissect them unless they are immersed in water during the operation4 ,if the object is opaque and must be worked by reflected light1 a small square trough may be made to the required size of gutta-percha1 which substance will not injure the edge of the knives1 c42 but where transparency is necessary1 a piece of thin plate-glass must be taken1 and by the aid of marine glue 7as explained in ,chapter ,,iv47 the sides affixed of the required depth4 ,as pins1 c41 cannot be used with the glass troughs and the substance must be kept extended1 a thin sheet of cork loaded with lead in order to keep it under water may be used2 but this1 of course1 renders the bottom opaque4 ,when working with many thin substances1 a plate of glass three or four inches long and two wide will serve every purpose1 and be more pleasant to use than the trough4 ,a drop or two of water will be as much liquid as is needed1 and this will lie very well upon the flat surface4 ,as these are the principal apparatus and arrangements which are requisite in dissection1 the method of proceeding in a few cases may now be noticed4 ,,vegetables4--,the dissection of vegetable matter is much less complicated than that of animal2 maceration in water being a great assistant1 and in many cases removing all necessity for the use of the knife4 ,this maceration may be assisted by needles1 and portions of the matter which are not required may be removed by them4 ,when1 for instance1 the spiral vessels which are found in rhubarb are wanted1 some parts containing these are chosen and left in a small quantity of water until the mass becomes soft1 and this is more quickly effected when the water is not changed4 ,the mass must be then placed upon a glass plate when practicable1 or in the trough when large1 and with the aid of two needles the matter may be removed from the spiral vessels1 which are plainly seen with a comparatively low power2 and by conveying these to a clean slip of glass1 repeating the process1 and at last washing well1 good specimens may be procured4 ,most of these should be mounted in some of the preservative liquids in the manner described in ,chapter ,,iv4 ,many1 however1 may be dried on the slide1 immersed in turpentine1 and then mounted in balsam2 but liquid is preferable1 as it best preserves the natural appearance4 ,certain kinds of vegetables require a different treatment to separate these spiral vessels4 ,asparagus is composed of very hard vegetable matter1 and some have recommended the stems to be first boiled1 which will soften them to such a degree that they may easily be separated4 ,dilute acids are also occasionally used to effect this2 and in some instances to obtain the raphides caustic potash may be employed2 but after any of these agents have been made use of1 the objects must be thoroughly cleansed with water1 else the dissecting instruments 7and perhaps the cell7 will be injured by the action of the remaining portion of the softening agent4 ,for the dissection of animal tissues it is necessary that the instruments be in the best order as to sharpness1 c42 and as the rules to be observed must necessarily be somewhat alike in many instances1 the treatment required by some of the objects most frequently mounted will now be described4 ,we may here remark that cartilage can be best examined by taking sections1 which will show the arrangement of the cells very perfectly4 ,this1 however1 is plainly seen in the mouse's ear without any section being necessary4 ,glycerine1 the preservative liquids before mentioned1 and ,canada balsam are all used to mount it2 but perhaps the first named may be preferred in many cases4 ,,muscle4--,this is what is commonly called the 8flesh0 of animals4 ,if a piece be laid upon the slide under the microscope1 bundles of 8fibres0 will be perceived1 which with needles and a little patience may be separated into portions1 some of these being 8striated10 or marked with alternate spaces of dark and light4 ,some of the non-striated or smooth class of muscle1 such as is found in intestines1 may be prepared for the microscope by immersing for a day or two in nitric acid diluted with three or four parts of water1 and then separating with needles and mounting as soon as possible4 ,sometimes boiling is resorted to to facilitate the separation1 and occasions little or no alteration in the material4 ,specimens are often taken from the frog and the pig1 as being amongst the best1 ,goadby's solution being generally used in mounting them4 ,the muscle of insects also shows the stri very perfectly4 ,,nerve-,,tissue4--,this is seldom mounted2 as ,dr4 ,carpenter observes1 8no method of preserving the nerve-tissue has been devised which makes it worth while to mount preparations for the sake of displaying its minute characters10 but we will mention a few particulars to be observed in its treatment4 ,the nerve should be taken from the animal as soon as possible after death1 and laid upon a glass slide1 with a drop or two of serum if possible4 ,the needles may be used to clean it1 but extreme delicacy is necessary4 ,it will be found that the nerve is tubular and filled with a substance which is readily ejected by very slight pressure4 ,when the nerve is submitted to the action of acetic acid1 the outer covering1 which is very thin1 is considerably contracted1 whilst the inner tube is left projecting2 and thus is most distinctly shown the nature of the arrangement4 ,mr4 ,lockhart ,clarke1 who has made great researches into the structure of the spinal cord1 gives a part of his experience as follows3--,he takes a perfectly fresh spinal cord and submits it to the action of strong spirits of wine4 ,this gives the substance such a degree of hardness that thin sections may be readily cut from it1 which should be placed upon a glass in a liquid consisting of three parts of spirit and one of acetic acid1 which renders them very distinct4 ,to mount these sections1 they must now be steeped in pure spirit for two hours and afterwards in oil of turpentine1 and lastly must be mounted in ,canada balsam4 ,,trache ,,of ,,insects1 ,c4--,the nature of these was described in ,chapter ,,iii41 but the method of procuring them was not explained1 as this clearly belongs to 8dissection40 ,the larger tubes are readily separated by placing the insect in water1 and fixing as firmly as possible1 when the body must be opened and the viscera removed4 ,the trache may then be cleaned by the aid of a camel-hair pencil1 and floated upon a glass1 where they must first be allowed to dry1 and then be mounted in balsam4 ,mr4 ,quekett gives the following method of removing the trache from the larva of an insect3--8,make a small opening in its body1 and then place it in strong acetic acid4 ,this will soften or decompose all the viscera1 and the trache may then be well washed with the syringe1 and removed from the body with the greatest facility1 by cutting away the connections of the main tubes with the spiracles by means of fine-pointed scissors4 ,in order to get them upon the slide1 it must be put into the fluid1 and the trache floated upon it2 after which they may be laid out in their proper position1 then dried and mounted in balsam40 ,if we wish them to bear their natural appearance1 they must be mounted in a cell with ,goadby's fluid2 but the structure is sometimes well shown in specimens mounted dry4 ,as before mentioned1 these trache terminate on the outside in openings termed spiracles1 which are round1 oblong1 and of various shapes4 ,over these are generally a quantity of minute hairs1 forming a guard against the entrance of dust1 c4 ,the forms of these are seldom alike in two different kinds of insects1 so that there is here a wide field for the student4 ,the dissection1 moreover1 is very easy1 as they may be cut from the body with a sharp knife or scissors1 and mounted in balsam or fluid4 ,many of the larv afford good specimens1 as do also some of the common ,coleopterous insects4 ,,tongues1 ,,or ,,palates1 ,,of ,,molluscs4--,of the nature of these1 ,dr4 ,carpenter gives the following description3--8,the organ which is commonly known under this designation is one of a very singular nature2 and we should be altogether wrong in conceiving of it as having any likeness to that on which our ordinary ideas of such an organ are founded4 ,for1 instead of being a projecting body1 lying in the cavity of the mouth1 it is a tube that passes backwards and downwards beneath the mouth1 its higher end being closed1 whilst in front it opens obliquely upon the floor of the mouth1 being1 as it were1 slit up and spread out so as to form a nearly flat surface4 ,on the interior of the tube1 as well as on the flat expansion of it1 we find numerous transverse rows of minute teeth1 which are set upon flattened plates2 each principal tooth sometimes having a basal plate of its own1 whilst in other instances one plate carries several teeth40 ,these palates1 or tongues1 differ much amongst the ,gasteropods in form and size1 some of them being comparatively of an immense length4 ,many are amongst the most beautiful objects when examined with polarized light4 ,they must1 however1 be procured by dissection1 which is usually performed as follows3--,the animal is placed on the cork in the dissecting-trough before mentioned1 and the head and forepart cut open1 spread out1 and firmly pinned down4 ,with the aid of fine scissors or knife1 the tongue must be then detached from its fastenings1 and placed in water for a day or two1 when all foreign matter may with a little care be removed4 ,in what way it should be mounted will depend on the purpose for which it is intended4 ,if for examination as an ordinary object1 it may be laid upon the slide and allowed to dry1 which arrangement will show the teeth very well4 ,if we wish to see it as it is naturally1 it must be mounted in a cell with ,goadby's fluid2 but if it is wanted as a polarizing object1 it must be floated upon a slide1 allowed to dry thoroughly1 and then ,canada balsam added in the usual manner4 ,in the stomach1 also1 of some of these molluscs teeth are found1 which are very interesting objects to examine1 and must be dissected out in the same manner as the 8tongues40 ,since writing the above4 ,dr4 ,alcock 7whose very beautiful specimens prove him to be a great authority in this branch7 has published some of his experience in the second volume of the third series of 8,memoirs of the ,literary and ,philosophical ,society of ,manchester40 ,by his permission ,i make the following extract3-- 8,this closes my present communication on the tongues of mollusca2 but as some members may possibly feel inclined to enter upon the inquiry themselves1 ,i think it will not be amiss to add a few remarks on the manner in which they are to be obtained4 8,first1 as to the kinds best worth the trouble of preparation4 ,whelks1 ,limpets1 and ,trochuses should be taken first4 ,land and fresh-water snails can scarcely be recommended1 except as a special study1--their tongues being rather more difficult to find1 and the teeth so small that they require a high power to show them properly4 ,it would appear1 from ,spallanzani's description of the anatomy of the head of the snail1 that even he did not make out this part1 although1 in his curious observations on the reproduction of lost parts1 he must have carefully dissected more snails than any other man4 8,as to preserving the animals till wanted1 they should simply be dropped alive into glycerine or alcohol4 ,glycerine is perhaps best where only the tongues are wanted2 but it leaves the animals very soft2 and as it does not harden their mucus at all1 they are very slippery and difficult to work upon when so preserved4 8,then as to the apparatus required for dissection4 ,in the first place1 all the work is to be done under water1 and a common saucer is generally the most convenient vessel to use4 ,no kind of fastening down or pinning out of the animal is needed2 and1 in fact1 it is much better to have it quite free1 that you may turn it about any way you wish4 ,the necessary instruments are a needle-point1 a pair of fine-pointed scissors1 and small forceps2 the forceps should have their points slightly turned in towards each other4 8,a word or two on the lingual apparatus generally1 and on its special characters in a few different animals1 will conclude what ,i have to say4 8,the mode of using the tongue can be easily seen in any of the common water-snails1 when they are crawling on the glass sides of an aquarium2 it may then be observed that from between the fleshy lips a thick mass is protruded1 with a motion forwards and upwards1 and afterwards withdrawn1 these movements being almost continually repeated4 ,the action has the appearance of licking2 but when the light falls suitably on the protruded structure1 it is seen to be armed with a number of bright points1 which are the lingual teeth1 so arranged as to give the organ the character and action of a rasp4 8,if you proceed to dissection1 and open the head of one of these mollusca 7say1 for instance1 a common limpet71 you will find the cavity of the mouth almost filled with the thick fleshy mass1 the front of which is protruded in the act of feeding2 and on its upper surface1 extending along the middle line from back to front1 is seen the strong membranous band upon which the teeth are set4 ,the mass itself consists of a cartilaginous frame1 surrounded by strong muscles2 and these structures constitute the whole of the active part of the lingual apparatus4444 8,but the peculiarity of the toothed membrane1 which makes its name of #8ribbon' so appropriate1 is1 that there is always a considerable length of it behind the mouth1 perfectly formed1 and ready to come forward and supply the place of that at the front1 which is continually wearing away by use4 8,in the limpet this reserve-ribbon is of great length1 being nearly twice as long as the body1 and the whole of it is exposed to view on simply removing the foot of the animal2 nothing1 then1 can be easier than to extract the tongue of the common limpet4 ,but1 unfortunately1 what you find in one kind of mollusc is not at all what you find in another4 ,in the ,acmas1 for instance1 which are very closely related to the limpets1 and have shells which cannot be distinguished1 the reserve portion of the ribbon has to be dug out from the substance of the liver1 in which it is imbedded1 that organ being1 as it were1 stitched completely through by a long loop of it4444 ,it might be thought a comfortable reflection that1 at all events1 one end of the ribbon can always be found in the mouth2 but in many cases this is about the worst place to look for it4 ,perhaps it may appear strange that in some of the smaller species1 with a retractile trunk1 a beginner may very likely fail altogether in his attempt to find the mouth2 if1 however1 the skin of the back is removed1 commencing just behind the tentacles1 there will be very little difficulty in making out the trunk1 which either contains the whole of the ribbon1 as in the whelk1 or the front part of it1 as in ,purpura and ,murex1 where a free coil is also seen to hang from its hinder extremity4444 ,in the periwinkles the same plan of proceeding1 by at once opening the back of the animal1 is best2 and on doing so1 the long ribbon1 coiled up like a watch-spring1 cannot fail to be found4 8,in the ,trochuses1 and indeed in all the ,scutibranchiata1 one point of the scissors should be introduced into the mouth of the animal1 and an incision made directly backwards in the middle line above to some distance behind the tentacles2 the tongue is then immediately brought into view1 lying along the floor of the mouth40 ,dr4 ,alcock's method of dissection will be found to differ in some degree from the general rules before given2 and when the tongue is dissected out he washes it for one hour 7shaking it now and then7 in a weak solution of potash4 ,after cleaning thoroughly in water1 it must be mounted by one of the methods before mentioned4 ,amongst insects1 especially the grasshopper tribe1 are found many which possess a gizzard1 armed with strong teeth1 somewhat similar to those of the molluscs4 ,it requires great nicety of manipulation to obtain these for the microscope2 but it would be useless to attempt any description of the process here1 as the strident can only be successful by experience in dissecting objects less difficult to manage1 and by using the most delicate instruments4 ,we have now considered most of those objects which require any peculiar treatment in section-cutting1 c42 but in no branch of microscopic manipulation is experience more necessary than in this4 ,,chapter ,,vi4 ,,injection4 #a4 ,injection is the filling of the arteries1 veins1 or other vessels of animals with some coloured substance1 in order that their natural arrangement may be made visible4 ,this is1 of course1 a delicate operation1 and needs special apparatus1 which ,i will now attempt to describe4 #b4 ,syringe4--,this is usually made to contain about two ounces4 ,on each side of the part next to the handle is a ring1 so that the finger may be thrust through it1 and the thumb may work the piston as in an ordinary syringe4 ,the plug of the piston must be 8packed0 with wash-leather1 and fit so closely as to be perfectly air-tight2 and if1 when it has been used awhile1 it is found that some of the liquid escapes past the plug into the back part of the body1 it must be repacked1 which operation will be best understood by examining the part4 ,these syringes are made of various sizes1 but in ordinary operations the above will be all that is needed4 ,the nozzle is about an inch long1 and polished so accurately that there is no escape when the pipes are tightly placed upon it dry4 #c4 ,the pipes are usually about an inch long1 to the end of which are affixed thicker tubes so as to fit the nozzle1 as before mentioned1 whilst a short arm projects from each side of these1 so that the silk or thread which is used to tie this artery1 c41 upon the thin pipe may be carried round these arms1 and all danger of slipping off prevented4 ,the pipes are made of different sizes1 from that which will admit only a very fine needle 7and this will need now and then to be cleaned1 or to be freed from any chance obstruction71 to that which will take a large pin4 ,these sizes must always be at hand1 as the vessels of some subjects are exceedingly minute4 #d4 ,stopcock4--,this is a short pipe like a small straight tap1 which fits accurately upon the end of the syringe like the pipes1 and also takes the pipes in the same manner4 ,the use of this is absolutely necessary when the object is so large that one syringe full of liquid will not fill it4 ,if no preventive were used1 some part of the liquid would return whilst the syringe was being replenished1 but the stopcock is then turned as in an ordinary tap1 and all danger of this effectually removed4 #e4 ,curved needles4--,these are easily made by heating common needles at the end where the eye is situated1 and bending them with a small pair of 8pliers0 into a segment of a circle half an inch in diameter4 ,they are1 perhaps1 more convenient when the bent part is thrown slightly back where it commences4 ,the pointed end is then thrust into a common penholder1 and the needle needs no re-tempering1 as the work for which it is wanted is simply to convey the thread or silk under any artery or vessel where it would be impossible to reach with the unassisted fingers4 #f4 ,a kind of forceps1 commonly know by the name of 8bullnose forceps10 will be constantly required during the process of injecting4 ,these are short1 usually very strong1 but not heavy1 and close very tightly by their own spring1 which may be easily overcome and so released by the pressure of the fingers4 ,when any vessel has not been tied by the operator1 and he finds the injected fluid escaping1 one of these 8bulldogs0 may be taken up and closed upon the opening4 ,this will cause very little interruption1 and the stoppage will be almost as effectual as if it were tied4 #g4 ,when the ordinary mode of injection is employed1 it is necessary that the preparations be kept warm during the time they are used1 otherwise the gelatine or size which they contain becomes stiff1 and will not allow of being worked by the syringe4 ,for this purpose we must procure small earthenware or tin pots of the size required1 which will differ according to the kind of work to be done2 and to each of these a loose lid should be adapted to protect it from dust1 c4 ,these pots must be allowed to stand in a tin bath of water1 under which a lamp or gas flame may be placed to keep the temperature sufficiently high to insure the perfect fluidity of the mixture4 ,the tin bath is1 perhaps1 most convenient when made like a small shallow cistern2 but some close it on the top to place the pots upon it1 and alter the shape to their own convenience4 #h4 ,we will now inquire into some of the materials which are needed in this operation2 the first of which is size4 ,this substance is often used in the form of glue1 but it must be of the very best and most transparent kind4 ,to make the liquid which is to receive the colours for the usual mode of injecting1 take of this glue seven ounces1 and pour upon it one quart of clean water2 allow this to stand a few hours1 and then boil gently until it is thoroughly dissolved1 stirring with a wooden or glass rod during the process4 ,take all impurities from the surface1 and strain through flannel or other fine medium4 ,the weather affects this a little as to its stiffness when cold1 but this must be counteracted by adding a little more glue if found too liquid4 #i4 ,instead of glue1 gelatine is generally used1 especially when the work to be accomplished is of the finer kind4 ,the proportions are very different in this case1 one ounce of gelatine to about fourteen ounces of water being sufficient4 ,this1 like glue1 must be soaked a few hours in a small part of the cold water1 the remainder being boiled and added1 when it must be stirred until dissolved4 ,a good size may be made by boiling clean strips of parchment for awhile1 and then straining the liquid whilst hot through flannel2 but when the injections are to be transparent1 it is of the greatest importance that the size be as colourless as possible4 ,for this purpose good gelatine must be employed1 as ,nelson's or ,cox's3 some persons of experience prefer the latter4 #aj4 ,colours4--,the size-solution above mentioned will need some colouring matter to render it visible when injected into the vessels of any animal1 and different colours are used when two or more kinds of vessels are so treated1 in order that each 8set0 may be easily distinguished by sight4 ,the proportion in which these colours are added to the size-solution may be given as follows3-- #aa4 ,for-- ,red #h parts of size-solution 7by weight7 to #a part of vermilion4 ,yellow #f 0 0 #a 0 chrome yellow4 ,white #e 0 0 #a 0 flake-white4 ,blue #c 0 0 #a 0 blue-smalt1 fine4 ,black #ab 0 0 #a 0 lamp-black4 ,whichever of these colours is made use of must be levigated in a mortar with the addition of a very small quantity of water until every lump of colour or foreign matter is reduced to the finest state possible1 otherwise in the process of injecting it will most likely be found that some of the small channels have been closed and the progress of the liquid stopped4 ,when this fineness of particles is attained1 warmth sufficient to render the size quite fluid must be used1 and the colour added gradually1 stirring all the time with a rod4 ,it may be here mentioned that where one colour only is required1 vermilion is1 perhaps1 the best2 and blue is seldom used for opaque objects1 as it reflects very little more light than black4 #ab4 ,when it is wished to fill the capillaries 7the minute vessels connecting the arteries with the veins71 the 8,micrographic ,dictionary0 recommends the colouring matter to be made by double decomposition4 ,as a professed handbook would be1 perhaps1 deemed incomplete without some directions as to the mode of getting these colours1 ,i will here make use of those given in that work4 ,for red1 however1 vermilion1 as above stated1 may be used2 but it must be carefully examined by reflected light to see whether it be free from all colourless crystals or not4 ,it must first be worked in a mortar1 and then the whole thrown into a quantity of water and stirred about2 after leaving it not longer than a quarter of a minute1 the larger portions will settle to the bottom1 and the liquid being poured off will contain the finer powder4 ,this may then be dried slowly1 or added to the size whilst wet in the manner before advised4 #ac4 ,yellow injection4--,to prepare this1 take-- ,acetate 7sugar7 of lead #chj grains4 ,bichromate of potash #aeb 0 ,size #h ounces4 ,dissolve the lead salt in the warm size1 then add the bichromate of potash finely powdered4 ,some of the chromic acid remains free1 and is wasted in this solution1 so the following is given3-- ,acetate of lead #aij grains4 ,chromate of potash 7neutral7 #ajj 0 ,size #d ounces4 ,the first of these has the deepest colour1 and is the most generally used4 #ad4 ,white injection4--,this is a carbonate of lead3-- ,acetate of lead #aij grains4 ,carbonate of potash #hc 0 ,size #d ounces4 ,dissolve the acetate of lead in the warm size1 and filter through flannel2 dissolve the carbonate of potash in the smallest quantity of water1 and add to the size3 #adc grains of carbonate of soda may be substituted for the carbonate of potash4 #ae4 ,for blue injection1 which is not1 however1 much used with reflected light1 as before stated1 take-- ,prussian blue #gc grains4 ,oxalic acid #gc 0 ,size #d ounces4 ,the oxalic acid is first finely powdered in a mortar1 the ,prussian blue and a little water added1 and the whole then thoroughly mixed with the size4 #af4 ,it may here be repeated1 that it is only when the capillaries are to be filled that there is any need to be at the trouble to prepare the colours by this double decomposition2 and1 indeed1 colours ground so finely may be procured that the above instructions would have been omitted1 had it not been supposed that some students might find a double pleasure in performing as much of the work as possible by their own unaided labours4 #ag4 ,the process of injection may now be considered2 but it is impossible for written instructions to supply the place of experience4 ,i will do my best1 however1 to set the novice at least in the right way4 ,there are two kinds of injection--one where the object and colours are opaque1 and consequently fit for examination by reflected light only2 the other1 where the vessels are filled with transparent colours1 and must be viewed by transmitted light4 ,the first of these is most frequently employed1 so we will begin with it4 ,in the object which is to be injected a vessel of the kind which we wish to be filled must be found2 an opening must then be made in it to allow one of the small pipes before mentioned to be thrust some distance within it4 ,when this is accomplished1 thread the curved needle with a piece of silk thread1 or very fine string1 which some operators rub well with beeswax4 ,this thread must not be too thin1 else there is danger of cutting the vessel4 ,the cord is then carried under the inserted pipe1 and the vessel bound tightly upon it1 the ends being brought up round the transverse arms1 and there tied2 so that all danger of accidentally withdrawing the pipe is obviated4 ,care must now be used in closing all the vessels which communicate with that where the pipe is placed lest the injecting fluid escape2 and this must be done by tieing them with silk4 ,should1 however1 any of these be left open by accident1 the bullnose forceps must be made use of1 as before recommended4 #ah4 ,the part to be injected must now be immersed in warm water1 not1 however1 above #ajj ,fahrenheit1 and be left until the whole is thoroughly warmed4 ,whilst this is being done1 the coloured size must be made ready by the pot being placed in the tin bath of warm water1 which must be of sufficient temperature 7about #aaj ,fahrenheit7 to keep it perfectly liquid4 ,for the same purpose1 the syringe is often tightly covered with two or three folds of flannel2 and1 indeed1 there is no part of the process which requires more attention4 ,if the substance to be injected is too hot1 it is injured2 whilst1 if any of the articles are too cold1 the gelatine1 or size1 loses a part of its fluidity1 and consequently cannot enter the minute parts4 ,when all is prepared1 the syringe1 with the stopcock attached1 should be warmed1 and then filled and emptied with the injecting fluid two or three times1 care being taken that the end of the syringe be kept beneath any bubbles which form upon the surface4 ,the syringe may then be filled1 and closely attached to the pipe which is tied in the vessel4 ,with a firm and steady pressure the piston must be forced downwards1 when the substance will be perceived to swell1 and the colour show itself in places where the covering is thin4 ,when the syringe is almost emptied of its contents1 the stopcock must be turned to prevent any escape of the injection from the subject4 ,it must then be refilled1 as in the first instance1 and the process repeated4 ,i say almost emptied1 because it is well not to force the piston of the syringe quite to the bottom1 lest the small quantity of air which frequently remains be driven into some of the vessels1 and the object be injured or quite ruined4 ,as the injection is proceeded with1 it will be found that the force required grows greater1 yet care must be taken not to use too much1 or the vessels will burst1 and render all the labour fruitless4 ,the movement of the piston must be occasionally so slow as to be almost imperceptible1 and for this reason it is sometimes marked with lines about one-eighth of an inch apart4 #ai4 ,of course1 during the whole process the injecting fluid and subject must be kept at a temperature high enough to allow the liquid to flow freely2 and the escape of a little of it need cause no fears to the student1 as it is almost impossible to fill any subject without some loss4 ,when the injected object has received sufficient fluid1 it should have a plump appearance1 owing to all the vessels being well filled4 ,the vessel must then be tied up where the pipe was inserted1 and the whole left in cold water two or three hours1 after which time it may be mounted2 but it may be well to notice a few things which the beginner ought to know before entering into that part of the process2 and he may be here informed that it is not necessary to mount the objects immediately1 otherwise it would be impossible for one person to make use of half of any large subject1 as it would be in a state of decay long before each part could have been examined and separated4 ,large pieces should be therefore immersed in equal parts of spirits of wine and water1 or glycerine1 which some think better still1 and thus preserved in bottles until time can be given to a closer examination4 #bj4 ,in operating upon large subjects1 entire animals1 c41 the constant pressure required by the piston of the syringe grows wearisome1 besides occupying both hands1 which is sometimes inconvenient when working without assistance4 ,to obviate this1 another way of driving the syringe was published in the 8,micrographic ,dictionary0 which ,i will quote here3--8,we have therefore contrived a very simple piece of apparatus1 which any one can prepare for himself1 and which effects the object by mechanical means4 ,it consists of a rectangular piece of board1 two feet long and ten inches wide1 to one end of which is fastened an inclined piece of wood 7equal in width to the long board1 and one foot high74 ,the inclined portion is pierced with three holes1 one above the other1 into either of which the syringe may be placed--the uppermost being used for the larger1 the lowermost for the smaller syringe2 and these holes are of such size as freely to admit the syringe covered with flannel1 but not to allow the rings to pass through them4 ,the lower part of the syringe is supported upon a semiannular piece of wood1 fastened to the upper end of an upright rod1 which slides in a hollow cylinder fixed at its base to a small rectangular piece of wood2 and by means of a horizontal wooden screw1 the rod may be made to support the syringe at any height required4 ,the handle of the syringe is let into a groove in a stout wooden rod connected by means of two catgut strings with a smaller rod1 to the middle of which is fastened a string playing over a pulley1 and at the end of which is a hook for supporting weights1 the catgut strings passing through a longitudinal slit in the inclined piece of wood40 ,when in use the syringe is filled with injecting fluid1 and passed through one of the three holes which is most suitable4 ,the object being placed so that the pipe and syringe can be best joined1 the rod and strings are set in order1 and a weight placed on the hook4 ,the stopcock must then be opened gradually1 when the operator will be able to judge whether the weight is a proper one or not3 if the piston is driven with any speed1 there is danger of injuring the subject1 and less weight may be used2 if1 however1 the piston does not move1 more must be added4 #ba4 ,such is the method recommended by the 8,micrographic ,dictionary10 and perhaps it is as good as any mechanical plan could be2 but where the operator is willing to undergo the labour of performing all this with the hand1 he has a much better chance of succeeding1 because the pressure can be regulated so accurately1 and changed so quickly when requisite1 that no mere machine can compete with it1 however well contrived4 #bb4 ,when the beginner attempts to inject a subject1 one of his difficulties is finding the vessel from which to commence4 ,another consists in distinguishing the arteries from the veins2 but this is partly removed by making a longitudinal incision in the vessel1 and with a blunt thick needle probing a little distance into the tube4 ,the artery will be found thicker in the coating than the vein1 and the difference is easily perceived by this mode of testing3 the vein is also of a bluer colour than the artery4 ,i say above1 a 8longitudinal incision0 must be made3 the reason for this is1 the artery when cut across contracts considerably1 and is lost in the adjoining substance2 but where the opening is made longitudinally all danger of this contraction is obviated4 #bc4 ,the different systems of vessels are often injected with various colours1 so that their relative positions1 c41 may be shown most clearly4 ,in some specimens1 the veins are injected with white1 and the arteries with red2 in the kidney1 the urinary tubes are often filled with white1 and the arteries with red4 ,then1 again1 the liver affords tubes for three or four colours4 ,but no written instructions on this point can benefit the young student1 and he must be content for a while to employ himself with single colours until he has gained the mechanical skill and the primary knowledge which are necessary before he can make any advance4 #bd4 ,we will now consider the best methods of mounting injected objects4 ,they must always be well washed in water after they have been kept in any preservative liquid1 using a camel-hair pencil to clean the surface if necessary4 ,many parts when injected are in masses1 such as the lungs1 liver1 c41 of animals1 and consequently sections of these must be cut4 ,for this purpose ,valentine's knife is very convenient1 as the thickness can be regulated so easily2 but where the injections are opaque1 there is no need to have the sections very thin4 ,some few of this kind undergo comparatively little change in drying1 so that the section may be well washed and floated upon the glass slide in the place desired1 where it will dry perfectly and adhere to it4 ,it must be then moistened with turpentine and mounted in ,canada balsam like other objects4 ,no great heat should be used with these preparations1 as it is very liable to injure them2 and some of the colours seem to suffer a slight contraction when any great degree of warmth is applied4 ,there are many objects1 however1 which must be seen in the mass to be understood1 and1 indeed1 lose all their form and beauty in drying1 such as certain parts of the intestines1 c4 ,these must be mounted in fluid1 with the precautions noticed at length in ,chapter ,,iv41 and for this purpose either ,goadby's fluid1 the chloride of zinc solution1 or spirit diluted with ten parts of distilled water1 may be employed4 ,it is a good thing1 when practicable1 to mount similar objects on two separate slides1 using different preservative liquids1 and taking the precaution of marking each with the kind of liquid employed4 ,this not only serves as a guide to what is best for certain subjects1 but if one is injured1 there will probably be a good specimen in the other4 #be4 ,it may be here mentioned that many are now mounting sections of injected substances with the balsam and chloroform before mentioned1 instead of using balsam alone1 and consider that the labour is much lessened thereby4 #bf4 ,a description of that mode of injection which is most generally employed has now been given1 but this is not the only method of effecting our object4 ,a most ingenious process was invented by ,m4 ,doyers1 requiring no artificial warmth1 by which many beautiful objects have been prepared4 ,make a solution of bichromate of potash1 #ebd grains to a pint of water1 and throw this into the vessels to be injected2 then take #a1jjj grains of acetate of lead dissolved in half a pint of water1 and force this into the same vessels4 ,a decomposition now takes place in the vessels1 and the yellow chromate of lead is formed4 ,in this decomposition1 however1 the acetate of potash also is formed and as this salt has an injurious action upon the cells1 ,dr4 ,goadby recommends nitrate of lead to be used1 which preserves rather than destroys them4 ,he also advises the addition of two ounces of gelatine dissolved in eight ounces of water1 to eight ounces of the saturated solution of each salt2 but with this addition the hot-water bath would be required to keep the injecting fluid liquid4 #bg4 ,many of these are best mounted in balsam1 in the same manner as those made in the ordinary way2 whilst others are best shown when preserved in liquids1 for which purpose ,goadby's fluid may be employed4 #bh4 ,this mode of making injections with chromate of lead is deemed by many the best1 especially where one colour only is employed4 ,but it must be allowed that there is a little more danger of failure where two separate fluids are used for the same vessels4 #bi4 ,we will now consider the best manner of making transparent injections1 which1 for many purposes1 possess an undoubted advantage over the opaque ones4 ,but it must be remembered that there are certain subjects to which no transparent injection could be applied1 as they are too thick when in their natural state1 and cutting would destroy all that beauty which is shown by the different parts in their relative adaptation4 ,for those objects1 however1 which must be cut into sections to display their wonders1 or are naturally thin--such as some of the finer tissues1 livers1 kidneys1 c4--transparency is a great acquisition1 and enables us to understand the arrangement of the vessels more perfectly4 ,again1 another advantage is the simplicity of the process2 no hot water is needed with some preparations1 either for the subject or the injecting fluid1 which runs into the minute vessels thoroughly and easily1 whilst the cost is small4 #cj4 ,for this kind of injection no colour is so commonly made use of as ,prussian blue4 ,it is not a good one1 as was before stated1 for any opaque object1 as the light reflected from it appears almost black2 yet by transmitted light no colour is more useful1 because its distinctness is equally great by artificial light and ordinary daylight4 ,the method of preparing this1 as given by ,dr4 ,beale1 is as follows3-- ,glycerine #a ounce4 ,wood naphtha1 or pyroacetic acid #a drachm4 ,spirits of wine #a ounce4 ,ferrocyanide 7yellow prussiate7 of potash #ab grains4 ,tincture of sesquichloride of iron #a drachm4 ,water #d ounces4 ,dissolve the ferrocyanide of potash in one ounce of the water2 add the tincture of sesquichloride of iron to another ounce4 ,mix these solutions gradually together1 shaking the bottle well which contains them--it is best to add the iron to the potash solution4 ,when thoroughly mixed1 these solutions should produce a dark-blue mixture1 perfectly free from any perceptible masses or flocculi4 ,next mix the naphtha and spirits of wine1 and add the glycerine and the remaining two ounces of water4 ,this must now be slowly mixed with the blue liquid1 shaking the whole well in a large bottle whilst the two come together4 ,the tincture of sesquichloride of iron is recommended1 because it can always be obtained of a uniform strength4 #ca4 ,dr4 ,turnbull used a mixture slightly different from the above1 which is made with the sulphate of iron3-- ,purified sulphate of iron #aj grains4 ,ferrocyanide of potassium #cb grains4 ,glycerine #a ounce4 ,pyroacetic acid #a drachm4 ,alcohol #a ounce4 ,water #d ounces4 ,dissolve the sulphate of iron in one ounce of the water1 gradually add the ferrocyanide of potassium dissolved in another ounce1 and proceed as above4 #cb4 ,dr4 ,beale also gives us the following carmine injection to be employed in the same way as the blue4,g ,take-- ,carmine #e grains4 ,glycerine1 with #h or #aj drops of hydrochloric acid ounce4 ,glycerine 7pure7 #a ounce4 ,alcohol #b drachms4 ,water #f drachms4 ,mix the carmine with a few drops of water1 and when well incorporated add about five drops of liquor ammoni4 ,to this dark-red solution about half an ounce of the glycerine is to be added1 and the whole well shaken in a bottle4 ,next1 very gradually pour in the acid glycerine1 frequently shaking the bottle during admixture4 ,test the mixture with blue litmus-paper1 and if not of a very decidedly acid reaction1 a few more drops of acid may be added to the remainder of the glycerine and mixed as before4 ,lastly1 mix the alcohol and water very gradually1 shaking the bottle thoroughly after adding each successive portion till the whole is mixed4 ,this fluid may be kept ready prepared1 and injections made very rapidly with it4 ,g ,when1 however1 it is desirable to cut very thin sections of the injected subject1 the carmine is sometimes added to a solution of fine gelatine--gelatine one part to water eight parts4 ,but the warm water and mode of proceeding which are used with the size solutions before described will be necessary in this case also4 #cc4 ,the method of making injections with these colours is the same as with the gelatine mixtures before described1 except that no heat is required1 and consequently most of the trouble removed4 ,the bottle of the fluid must be well shaken immediately before use2 and when the object is injected1 we must allow it to remain in a cool place for a few hours before cutting it4 ,thin sections of the subject may be cut with ,valentine's knife1 as before described1 and are very beautiful transparent objects4 ,some of the finer tissues1 also1 are shown much better by this mode of injection than by the opaque1 and are easily mounted by washing in clean water when first separated1 and floating upon a slide1 where they must be allowed to dry thoroughly4 ,they may then be immediately mounted in balsam1 or kept in the dry state until it is convenient to finish them2 but in many cases this keeping1 if too much prolonged1 will injure the object4 ,if it is desired to transfer the section to another slide1 it will be necessary to wet it thoroughly with water by the aid of a camel-hair pencil1 and then gently strip it off with the forceps4 ,when it is wished to preserve injected subjects in 8masses10 it must be done by immersion in spirit1 and the sections may be cut at leisure4 ,most of these transparent objects may be mounted in ,canada balsam2 but some recommend glycerine or glycerine jelly1 as allowing the use of a higher power in their examination1 and preserving them in a more natural form4 #cd4 ,a few subjects may be noticed which are very beautiful when injected1 and amongst these are the eyes of many animals4 ,they must be injected by the artery in the back part1 and when the blue transparent liquid is employed1 nothing can exceed the delicate beauty which some of the membrane bears4 ,it must1 however1 be dissected with care1 but well repays us for the trouble4 ,water-newts and frogs are not difficult subjects1 and in their skin and other parts are many interesting objects4 ,amongst the commoner animals--rats1 rabbits1 cats1 c4 c4--almost endless employment may be found1 making use either of portions or the whole animal at once4 ,the intestines of many of these are very beautiful4 ,we must divide them with a pair of scissors along the tube1 and cleanse them from all the matter2 the coating may then be laid upon a slide1 and any remaining impurity removed with a camel-hair pencil and water4 ,when dried it may be mounted in balsam1 and having been injected with the transparent blue1 its minute beauty is shown most perfectly4 ,in injecting a sheep's foot1 which is a good object1 the liquid should be forced into it until a slight paring of the hoof shows the colour in the fine channels there4 #ce4 ,when the lungs of small animals are injected1 the finest fluid must be used1 as some of the capillaries are so small that it is not an easy matter to fill them properly4 ,and before entering upon these subjects1 a certain proficiency in the mode of using the syringe1 c41 should be obtained by practising upon simpler parts4 #cf4 ,no subjects are more difficult to inject than fish1 owing to the extreme softness of their tissues4 ,dr4 ,hogg recommends the tail of the fish to be cut off1 and the pipe to be put into the divided vessel which lies just beneath the spinal column2 by which method beautiful injections may be made4 ,the gills1 however1 are the most interesting part as microscopic objects4 #cg4 ,these instructions may seem very imperfect to those who have had much experience in this branch2 but they will remember that their own knowledge was not gained from any written descriptions1 but was forced upon them by frequent failures1 some of which probably were very disheartening4 ,as ,i before stated1 it is very difficult 7if not impossible7 to accomplish much without some knowledge of anatomy4 #ch4 ,i may here mention that the transparent injections sent over from the ,continent are beautifully executed by ,hyrtl of ,vienna 7who states that the injected fluid is composed of gelatine and carmine71 ,dr4 ,oschatz of ,berlin1 the ,microscopic ,institute of ,wabern1 ,schaffer and ,co4 of ,magdeburg1 and others4 ,some of these will bear examining with a high power4 ,a friend informs me that he measured a vessel in a rat's tongue by ,hyrtl1 which was #a-gbjjth of an inch in diameter1 and had a clear outline with quarter-inch objective4 ,he has also made many experiments with the same materials1 but has as yet failed in producing perfectly distinct outlines1 there being a tendency of the colouring matter 7magenta1 carmine4 c47 to diffuse itself through the coats of the vessels into the surrounding tissues1 although he has varied the pressure from one half a pound to sixty pounds4 ,he believes the vessels are first washed out 7injected with warm water and pressure applied71 then some fluid introduced which renders the arteries impervious to the coloured fluid afterwards injected4 #ci4 ,he finds that after washing out the vessels as above1 the injecting fluid is much more easily introduced4 ,he has used a strong solution of gallic acid previously to injecting with the colouring matter 7in one experiment only71 and the result was satisfactory4 ,he puts the query1--,might not carbolic acid have a similar effect8 ,he has often used it with injections to preserve the specimens1 but not in sufficient quantity to act in the way indicated above4 ,since writing the above1 ,mr4 ,j4 ,g4 ,dale1 ,f4,c4,s41 and ,i have made numerous experiments with carmine injection1 and have at length been favoured with what we deem success4 ,some of the vessels in a kitten lately injected do not exceed #a-bjjjth of an inch in diameter1 and present a clear outline with one-fifth objective4 ,there is no extra-vasation1 neither does the colouring matter show any grain except when a very high power is employed4 ,the following is our process3-- ,take #ahj grains best carmine4 fluid ounce of ammonia1 commercial strength1 viz41 #jib1 or #ae ammonia meter4 #c or #d ounces distilled water4 ,put these into a small flask1 and allow them to digest without heat from twenty-four to thirty-six hours1 or until the carmine is dissolved4 ,then take a ,winchester quart bottle1 and with a diamond mark the spot to which sixteen ounces of water extend4 ,the coloured solution must be filtered into the bottle1 and to this pure water should be added until the whole is equal to sixteen ounces4 ,dissolve #fjj grains potash alum in ten fluid ounces of water1 and add to this1 under constant boiling1 a solution of carbonate of soda until a slight permanent precipitate is produced4 ,filter and add water up to sixteen ounces4 ,boil and add the solution to the cold ammoniacal solution of carmine in the ,winchester quart1 and shake vigorously for a few minutes4 ,a drop of this placed upon white filtering-paper should show no coloured ring4 ,if much colour is in solution the whole must be rejected1 because1 although it is possible to precipitate all the colouring matter by the addition of ammonia or alum1 it is not well to do so1 as the physical condition of the precipitate is thereby altered4 ,supposing the precipitation to be complete1 or very nearly so1 shake vigorously for at least half an hour1 and allow it to stand until quite cold4 ,the shaking must then be renewed for some time1 and the bottle filled up with pure water4 ,after allowing the precipitate to settle a day1 draw off the clear supernatant fluid with a syphon4 ,repeat the washing until the clear liquid gives little or no precipitate with chloride of barium4 ,so much water must be left with the colour at last that it shall measure forty fluid ounces4 ,for the injecting fluid take twenty-four ounces of the above coloured liquid1 and three ounces of good gelatine4 ,allow these to remain together twelve hours1 and then dissolve by the heat of a water bath2 after which it should be strained through fine muslin4 ,as this injecting fluid contains gelatine1 the hot water1 and other contrivances mentioned in a former part of the chapter1 will be necessary here also1 but no peculiar treatment will be required4 ,,chapter ,,vii4 ,,miscellaneous4 ,it must be evident to all readers that there are various objects of interest to the microscopist which cannot be properly placed amongst any of the forementioned classes1 but must not be omitted in such a guide as this professes to be4 ,of these may be mentioned the circulation of the blood in various animals1 the rotary motion of the fluid in many plants1 the best means of taking minute photographs1 c4 c4 ,perhaps the most interesting of these objects is the circulation of the blood through the finer vessels of various parts of the animals made use of for these purposes1 which parts1 it is evident1 must be very transparent to afford a perfect view of this phenomenon4 ,the web of the frog's foot is very frequently made use of1 but requires a certain arrangement1 which we will now describe4 ,a piece of thin wood 7,dr4 ,carpenter recommends cork7 is taken1 about eight inches long and three wide2 about an inch from one end is cut a hole1 half or three-quarters of an inch in diameter4 ,the body of the frog is then placed in a wet bag1 or wrapped in wet calico1 whilst the hind-foot projects2 the whole is then laid upon the piece of wood so that the foot1 which is left free1 may be extended over the hole4 ,the web must then be spread out1 and secured either by threads to small pins on the wood1 or the pins must be driven through the web into the wood1 and so kept in position4 ,a few bands of tape must be passed round the body1 the leg1 and the wood1 to prevent any disarrangement arising from the animal starting1 c4 ,care must be taken that the tape is not too tight1 else the circulation will be very slow or altogether stopped4 ,the wood must now be fixed upon the stage1 with the aperture under the object-glass3 this is sometimes done by simply binding it1 or a spring is fixed so as to accomplish the same object without so much trouble4 ,with a half-inch power the blood may now be seen to flow very distinctly4 ,the frog may be used for hours if care is taken to prevent the web from becoming dry1 by wetting it with a little water from time to time4 ,the piece of wood or cork upon which the frog is laid is often made to give place to the 8frog-plates10 supplied by opticians4 ,these are made of brass1 somewhat resembling the piece of wood above recommended1 but each maker's pattern differs according to his own taste4 ,the tongue of the frog is also sometimes used for the purpose of showing the circulation of the blood1 which is done in the following manner3--,the body is wrapped with the calico1 and made fast to the plate as before1 only the mouth of the frog is brought to the opening4 ,the tongue is then gently drawn out of the mouth and pinned down over the aperture1 when the circulation will be well shown4 ,but1 as ,dr4 ,carpenter observes1 the cruelty of this mode of treatment is so repulsive that it is unjustifiable4 ,tadpoles of the frog 7which1 of course1 are only obtainable in their season7 are good subjects for showing the circulation of the blood4 ,they are best suited for the microscope when about one inch long4 ,the tadpoles of the newt and toad also are equally suitable4 ,they may be placed in a very shallow glass trough with a little water1 and a narrow band of linen bound lightly round in some part not required for examination1 to keep them from moving2 or they may be laid upon a glass plate with a drop or two of water1 and a thin glass covering lightly bound upon it4 ,dr4 ,carpenter1 however1 places them first in cold water1 gradually adding warm until the whole becomes about #ajj1 when the tadpole becomes rigid1 whilst the circulation is still maintained4 ,i have not1 however1 found this necessary1 the thin glass accomplishing all that is desired4 ,the tail is generally the most transparent1 and shows the circulation best2 but in some of the newt larv the blood may be traced down to the very extremities if they are not too old4 ,mr4 ,whitney places the tadpole upon its back1 by which means the heart and other internal arrangements may be seen4 ,amongst fishes also may be found subjects for the same purpose1 but they seldom furnish as good examples as those before mentioned1 because the blood-vessels are not nearly so abundant1 as in the foot of the frog1 c4 ,the stickleback is1 however1 procurable almost in any place during the summer months1 and may be laid in a shallow trough1 loosely bound down as the tadpole4 ,the tail may be covered with a piece of thin glass to prevent him curling it to the object-glass4 ,the power needed with this will be about the same as with the other subjects--viz41 half to quarter inch object-glass4 ,it is not absolutely necessary to go to reptiles or fishes for this curious sight1 as some other animals serve very well4 ,in the wings of the common bat may be found a good subject4 ,these must be stretched out on something resembling the frog-plate before described1 when those parts near to the bones will show the largest vessels very clearly4 ,the ear of a young mouse is an illustration of the same phenomenon1 but it is very difficult to fix it in a good position1 as these animals are so very timid and restless4 ,amongst insects also the same law may be observed1 by placing them in the 8cage10 or 8live-box10 so as to keep them still1 but not to injure them by too much pressure4 ,in certain larv this is particularly well shown1 as that of the day-fly and plumed gnat2 but in some of these the blood is almost colourless4 ,in the wings also of many insects this circulation is well seen1 as in those of the common housefly2 but as these parts become dry in a few days1 the subject should not be more than twenty-four hours old4 ,somewhat approximating to the forementioned phenomenon1 is the 8rotation0 of fluid in the cells1 or1 as it is usually termed1 the circulation of the sap1 of plants4 ,this is shown in certain vegetable growths as a constant stream of thick fluid1 wherein small globules are seen2 which stream flows round the individual cells1 or up the leaf1 turning at the extremity1 and down again by a different but parallel channel4 ,there is little or no difficulty in showing this in many plants2 but some are1 of course1 better than others1 and require a different treatment2 we will1 therefore1 notice a few of these4 ,perhaps the best of all is the ,vallisneria spiralis1 which is an aquatic plant1 frequently grown in1 but not really belonging to1 this country4 ,as it somewhat resembles grass1 the leaf is not used in its natural state1 but a thin section cut lengthwise with a razor or other sharp instrument--this section1 however1 is much better when the outer surface has been first removed4 ,it should then be laid upon a slide with a drop or two of water1 and covered with a piece of thin glass4 ,often the cutting of the section seems to be such a shock to the leaf that no motion is visible for awhile1 but in a short time the warmth of an ordinary sitting-room will revive it1 and with a quarter-inch object-glass the currents will be rendered beautifully distinct4 ,where the 8stream0 is unusually obstinate the warmth may be slightly increased1 but too great heat destroys the movement altogether4 ,in the summer1 any of the leaves show this 8circulation0 very well2 but in the winter1 the slightly yellow ones are said to be the best4 ,the ,vallisneria requires to be cut in sections to show this 8circulation20 but there are many plants of which it is but necessary to take a fragment and lay it upon a slide4 ,the ,anacharis alsinastrum is one of these3 it grows in water1 having three leaves round the stem1 then a bare portion1 again another three leaves1 and so on4 ,one of these leaves must be plucked close to the stem1 and laid upon a slide with a drop of water4 ,thin glass should be placed upon it1 and along the mid-rib of the leaves the 8circulation0 may be seen most beautifully when a good specimen has been chosen2 but it requires rather more power than the ,vallisneria4 ,this plant is very common in many parts of the country1 a great number of our ponds and streams being literally choked up by it4 ,in the ,chara vulgaris and two or three of the ,nitell1 c41 this phenomenon may also be seen with no preparation except plucking a part from the stem and laying it upon a slide as with the ,anacharis4 ,in using the ,frog-bit1 the outer part of the young leaf-buds must be taken to obtain the best specimens for this purpose2 but a section of the stem will also show the 8circulation10 though not so well4 ,the plants before mentioned are all aquatic1 but the same movement of the globules has been observed in several kinds of land plants1 as in the hairs upon the leaf-stalks of the common groundsel2 but these do not show it so well1 nor are they so easily managed as the above4 ,many microscopists who are not fortunate enough to be in the neighbourhood of these plants 7indeed the ,vallisneria is a foreign one7 grow them in jars1 so a few remarks as to the treatment they require will not be out of place4 ,the ,vallisneria requires a temperature not lower than #ee or #fj1 and even a higher degree than this renders its growth quicker2 and no great change must take place3 the more equable the temperature the more healthy will the plant be4 ,a glass jar should be taken1 having an inch or two of mould at the bottom1 which must be pressed down closely1 and the plant must be set in this4 ,water must then be gently poured in1 so as not to disturb the mould4 ,as this plant flourishes best when the water is frequently changed1 ,mr4 ,quekett recommends that the jar should be occasionally placed under a tap of water1 and a very gentle stream allowed to fall into it for several hours1 by which means much of the confervoid growth will be got rid of and the plant invigorated4 ,the ,anacharis may be rooted in the earth like the ,vallisneria1 but a small detached piece may be thrown into the jar of water and there left until wanted4 ,for months the 8circulation0 will be well shown by it1 and it will probably grow and increase4 ,it is also very healthy in an in-door aquarium4 ,it is recommended that the jars in which any of the ,chara are grown should be moved about as little as possible1 as the long roots are very tender1 and will not bear agitation4 ,an object which is interesting to the microscopist1 as well as the unscientific observer1 is the growth of seeds1 as it is often erroneously termed4 ,a shaving of the outside of the seed is taken and laid upon the glass slide2 a thin glass cover is then placed upon it1 and a drop of water applied to the edge of this4 ,the water will then gradually flow under the glass and reach the section of the seed1 when the transparent fibres will appear to spring out and 8grow0 for some minutes4 ,this1 however1 is produced by the unfolding of a spiral formation in the cells1 and1 therefore1 has really no similarity to the true growth4 ,the seeds of the ,salvias1 ,collomias1 ,senecio1 ,ruellia1 c41 are well suited for the display of this curious sight4 ,to watch the development of the spores of ferns1 and the fertilization and products1 ,dr4 ,carpenter recommends the following mode of proceeding3--8,let a frond of a fern1 whose fructification is mature1 be laid upon a piece of fine paper1 with its spore-bearing surface downwards2 in the course of a day or two this paper will be found to be covered with a very fine brownish dust1 which consists of the discharged spores4 ,this must be carefully collected1 and should be spread upon the surface of a smoothed fragment of porous sandstone2 the stone being placed in a saucer1 the bottom of which is covered with water1 and a glass #8tumbler' being inverted over it1 the requisite supply of moisture is insured1 and the spores will germinate luxuriantly4 ,some of the prothallia soon advance beyond the rest2 and at the time when the advanced ones have long ceased to produce antheridia1 and bear abundance of archegonia1 those which have remained behind in their growth are beginning to be covered with antheridia4 ,if the crop be now kept with little moisture for several weeks and then suddenly watered1 a large number of antheridia and archegonia simultaneously open1 and in a few hours afterwards the surface of the larger prothallia will be found almost covered with moving antherozoids4 ,such prothallia as exhibit freshly opened archegonia are now to be held by one lobe between the forefinger and thumb of the left hand1 so that the upper surface of the prothallium lies upon the thumb2 and the thinnest possible sections are then to be made with a narrow-bladed knife perpendicularly to the surface of the prothallium4 ,of these sections1 which after much practice may be made no more than #a-aeth of a line of thickness1 some will probably lay open the canals of the archegonia1 and within these1 when examined with a power of #bjj or #cjj diameters1 antherozoids may be occasionally distinguished40 ,another interesting object to the young microscopist is afforded by the spores of the equiseta 7or horsetails1 as they are often called74 ,these may be obtained by shaking the higher portion of the stems when the spores are ripe4 ,they will then fall like small dust1 and may be placed under the microscope4 ,the spores are then seen to consist of a somewhat heart-shaped mass with bands rather intricately curled around it4 ,as they dry these bands expand1 and are seen to be four lines at right angles1 with the ends clubbed1 as it may be called4 ,if1 whilst watching them1 the spores are breathed upon1 these bands immediately return to their former state1 and are closely curled around the spore2 but as they gradually dry again expand4 ,this experiment may be repeated many times1 and is a very interesting one4 ,the above are the principal objects which could not possibly be included in any of the former chapters1 but would have left a most interesting branch untouched had it been neglected4 ,there is another subject also which should not be passed by--viz41 the production of minute pictures which serve as objects for microscopic examination4 ,i may here mention that as this manual is simply to enable the young student to prepare and mount his objects1 the photography of magnified objects has evidently no place here4 ,few slides caused so much astonishment as these minute photographs when first exhibited2 small spots were seen to contain large pictures1 and a page of printed matter was compressed into the one-hundredth part of a square inch4 ,it would be impossible in this place to give the inquirer any instruction in the manipulation of photography1 so it must be assumed that he already knows this4 ,we will first consider the process performed by artificial light4 ,the collodion employed in photographing generally shows as much structure when magnified as is found in linen of moderate texture2 but this is not always the case1 as some samples bear much enlargement without any of this appearance4 ,it is evident that a structure so coarse would make it entirely unfit for these minute pictures1 as all the small markings would be destroyed1 or so interfered with that no great enlargement would be practicable4 ,to obtain almost structureless collodion is not an easy matter1 and a clever practitioner in this branch of photography states that he knows of no method to accomplish this with certainty1 but he himself tries different samples until he falls upon a suitable one1 which he then lays aside for this object4 ,a beneficial effect is often derived from keeping the collodion awhile1 but this is not always the case4 ,the slides should be chosen of an equal thickness1 so that when focussed upon one no re-adjustment may be necessary for the others4 ,the glass should1 of course1 be free from any roughness1 scratches1 or other imperfections1 and of first-rate quality and colour4 ,the microscope must then be placed in a horizontal position1 and the eye-piece removed1 the stage having a small clip upon it to keep the prepared plate in position4 ,the negative must then be supported at a distance from the end of the microscope tube from which the eye-piece was withdrawn4 ,this distance will1 of course1 vary according to the relative sizes of the negative and desired picture4 ,with a one-inch object-glass1 which is a very convenient focus1 it will have to be changed usually betwixt one and four feet4 ,the negative must be lighted by an argand gas-burner or camphine-lamp1 and the rays rendered as parallel as possible by the use of a large lens placed betwixt the light and the negative4 ,it is not easy to arrange the apparatus so as to get the light uniform2 but a little practice will soon do away with this difficulty4 ,ordinary ground-glass is too coarsely grained to focus upon1 as the magnifying power used to examine the minute reflection must be considerable4 ,one of the slides must therefore be coated with the collodion1 submitted to the silver-bath1 and after washing with water be allowed to dry4 ,upon this may be focussed the reflected image1 and its minuteness examined with a powerful hand-magnifier1 or another microscope placed behind in a horizontal position4 ,when the utmost sharpness of definition is obtained1 it is usually required to remove the plate a little distance from the object-glass1 as object-glasses for the microscope are slightly 8over corrected10 and the chemical rays which accomplish the photography are beyond the visual ones4 ,the exact distance required to give a picture to bear the greatest enlargement cannot be given by rule2 but experiments must be made at first1 and it will always be the same with the object-glass which we have tested4 ,the plate may now be prepared as in ordinary photography1 and placed upon the stage whilst the light is shaded4 ,when all is ready1 the shade is removed and the process allowed to go on1 usually for thirty or forty seconds2 but no certain rule can be given as to the required time1 on account of various collodions1 lamps1 and powers being used4 ,it may be here mentioned1 that it is well to contrive some little frame to receive the prepared plate1 as the silver bath solution is liable to get upon the microscope stage and so1 to say the least1 disfigure it4 ,when the exposure has been continued sufficiently long1 the picture may be developed by any of the ordinary methods1 but some of the best productions have been brought out by the aid of pyrogallic and citric acid solution1 with the addition of a little alcohol4 ,the 8fixing0 may be effected by a strong solution of hypo-sulphite of soda1 and the picture must then be very well washed with pure water4 ,when dry1 the photograph must be mounted with ,canada balsam1 in the same manner as any ordinary object2 but great heat must not be used1 or the picture may be injured4 ,when ordinary daylight is employed for this purpose1 a dark slide will be required for the prepared plate1 in the same way as for photographing landscape1 c4 ,these dark slides are generally made by each individual to suit his particular arrangements of negatives1 c42 but it may be here recommended that the operator should always focus in the same slide which he is about to use1 as so small a difference in distance lies betwixt perfection and failure4 ,for an ordinary student1 perhaps the above method is that which is the most readily used1 and consequently the most generally available2 but almost every one has a different arrangement of microscope1 c41 by which he procures these minute pictures4 ,mr4 ,shadbolt 7one of our most successful photographers7 gives the following instructions3--8,having removed the upper stage plate of a large compound microscope1 ,i replace it with one of wood1 supplied with guide pins of silver wire1 in order to admit of its supporting a slip of glass coated with collodion1 and excited in the nitrate of silver bath in the usual way4 ,if the ordinary brass stage plate were left undisturbed1 it is obvious that it and the excited slip of glass would be mutually destructive4 8,the microscope is now to be placed in a horizontal position1 the objective1 intended to produce the picture1 made to occupy the place usually filled by the achromatic condenser on the sub-stage of the microscope1 while another objective is screwed into the lower end of the body of the instrument1 which is used not only to focus with1 but also to make the requisite allowance for actinic variation4 8,the negative intended to be reduced is then arranged vertically1 with its centre in the axis of the microscopic body1 at a distance of from two to four feet from the lower object-glass1 and with a convenient screen of card1 wood1 or thick paper1 to cut off any extraneous light that would otherwise pass beyond the limits of the picture4 8,a small camphine-lamp is employed for the purpose of illuminating the negative1 having a good bull's-eye lens as a condenser1 so arranged with its flat side next the lamp that the refracted rays shall just fill the whole of a double convex lens of about six inches in diameter1 the latter being placed in such a position as to refract the rays of light in a parallel direction upon the negative4 ,by this arrangement the bull's-eye lens of about two inches and a half in diameter appears as the source of the light instead of the small flame of the lamp4 8,by using a bat's-wing gas-burner of a good size1 a single lens1 instead of the two1 may be so placed as to give the necessary uniformity of illumination40 ,this arrangement requires the same care in working as that before mentioned1 the pictures being produced1 developed1 and fixed by the same treatment4 ,as before stated1 almost every manipulator makes some small changes in the method of producing these minute pictures2 but the rules given1 though far from new1 are sufficient for all purposes2 and ,i may state with truth1 that those which ,i procured when these wonders were quite new1 are fully equal in every respect to the best usually met with at the present time4 ,with these instructions ,i shall close my ,handbook1 as ,i believe that every branch of ,preparation and ,mounting of ,microscopic ,objects has been treated of4 ,not that the beginner can expect that he has nothing to do except read this to be able to mount everything2 but there are difficulties from which he may be freed by instruction1 when otherwise he would have been compelled to learn by failure alone4 ,i may1 here1 however1 repeat certain advice before given1--that1 when practicable1 it is a good thing to mount each object by two or more different methods1 as very frequently one feature is best shown dry1 another in liquid1 and a third in balsam4 ,secondly1 let the mounting be studied thoroughly1 as no part of the microscopic science is more worthy of thought than this4 ,and lastly1 let no failures prevent you following up what will assuredly one day become a source of great pleasure1 and render your daily 8constitutional walk10 which is often dull in the extreme1 very delightful1 as it will afford you some new wonder in every hedge-row4 ,,index4 ,air-bubbles1 #ef4 ,air-pump1 #ac2 use of1 #eg4 ,alcock1 ,dr41 on tongues of ,mollusca1 #aah4 ,alg1 mounting of1 #ia4 ,anacharis alsinastrum1 rotation in1 #adc2 to cultivate1 #add4 ,animal tissues1 dissection of1 #aad4 ,antenn of insects1 #ga2 in preservative liquid1 #id4 ,apparatus required in mounting objects1 i4 ,arteries1 how to distinguish1 in injection1 #aca4 ,asparagus1 spiral vessels of1 #aad4 ,asphaltum1 #ae2 and india-rubber1 as cement and varnish1 #ah4 ,bat1 circulation of blood in wings of1 #adb4 ,beale's1 ,dr41 ,prussian blue for injecting1 #acd2 carmine1 #ace4 ,bell-glasses1 use of1 #ab4 ,berg-mehl1 #dj4 ,bermuda earth1 #dj4 ,bichromate of lead1 injection with1 #acb4 ,bird1 ,dr4 ,golding1 on preparation of ,zoophytes1 #fe4 ,black-japan1 as a cement1 #af4 ,black varnish1 #ah4 ,blood1 as a microscopic object1 #ej2 circulation of1 #adj-adb4 ,bone1 sections of1 #ajb2 fossil1 #ajc4 ,brass plate for heating glasses1 c41 #ac4 ,cactace1 raphides of1 #eb4 ,camel-hair pencils1 use of1 #aj4 ,canada balsam1 #ad2 with chloroform1 #ad1 #fj1 #acb2 with turpentine1 #ad2 air bubbles in1 #ef2 ,dr4 ,carpenter's syringe for1 #ei2 to fill cells with1 #fj2 mounting of objects in1 #ef4 ,carbolic acid1 #hf4 ,carmine injecting fluid1 ,dr4 ,beale's1 #ace3 ,dale ,davies'1 #ach4 ,cartilage1 dissection of1 #aad4 ,castor oil1 as a preservative1 #hf4 ,cells for dry objects1 #f2 with rings of cardboard1 #g2 with gutta-percha1 #g2 with leather1 #g2 with ivory1 #h2 with thin glass1 #g2 with varnish1 #bc1 #bf2 for balsam1 #fj2 for preservative liquids1 #hg-hi2 ,shadbolt's turntable useful in making1 #i4 ,cements1 #ac-ag4 ,chalk1 foraminifera from1 #fc4 ,chara vulgaris1 rotation in1 #add4 ,chloride of zinc1 solution of1 #he2 of calcium1 solution of1 #ib4 ,chloroform1 use of 7see ,canada balsam74 ,circulation of blood1 #adj-adb2 of sap 7see ,rotation74 ,cleanliness in microscopic work1 #a4 ,coal1 sections of1 #ii4 ,collection of diatoms1 #bi4 ,colours for injection1 #abe-abg4 ,condenser1 cheap1 to make1 #bj4 ,corals1 sections of1 #ii4 ,corallines1 to mount1 #dh4 ,cover of objects1 to remove1 #fj4 ,crystals1 mounting of1 dry1 #ej2 to vary form of1 and mount in balsam1 #ge2 sections of1 #aji4 ,cuticle of equisetum1 c41 #hj4 ,dale ,davies'1 carmine injection1 #ach4 ,deane's gelatine1 #hd4 ,decalcifying process for shells1 #ih4 ,desmidiace1 in preservative liquid1 #ib4 ,diacha elegans1 #ec4 ,diamond beetle1 #ed4 ,diatomace1 nature of1 #bh2 collection of1 #bi2 in stomachs of fish1 #cj2 to prepare and mount dry1 #cj-dj2 ,mr4 ,rylands on1 #cc2 in guano1 #ci2 fossilized1 #dj2 mounting in balsam1 #fa2 mounting in preservative liquids1 #ib1 #ic4 ,discs used in mounting1 #bb2 supporter1 ,smith ,beck's1 #bc4 ,dissection1 #aaa2 microscope for1 #aaa2 instruments for1 #aab4 ,distilled water1 as preservative liquid1 #hc4 ,doyer's1 ,m41 method of injection1 #acb4 ,dry objects1 to mount1 #bb4 ,echinodermata spines1 sections of1 #ii4 ,eel1 scales of1 #gh4 ,eggs of insects1 #id4 ,elastic objects1 to keep flat upon the slide1 #aa4 ,electrical cement1 #af4 ,equisetace1 #hj2 spores of1 #adf4 ,erector1 not indispensable1 #ai4 ,eyes of insects1 #gj1 #ed2 of animals injected1 #acf4 ,feathers1 #gc4 ,feet of insects1 #ed1 #ga4 ,ferns1 #ea2 development of spores of1 #ade4 ,fish1 fins and tails of1 #ej2 scales of1 #ec1 #gh2 injection of1 #acg2 circulation of blood in1 #adb4 ,flint1 sections of1 #aja4 ,fluid1 mounting objects in1 #hc4 ,flustra avicularis1 #gi4 ,fly 7see ,insects74 ,foot of sheep injected1 #acf4 ,foraminifera1 #da2 separation of1 #da2 to clean1 #db2 to clean from tallow soundings1 #db2 to mount1 #de1 #fc2 from chalk1 #fc4 ,forceps1 ordinary and wooden1 #aa2 bull-nosed1 for injection1 #abc4 ,fossil infusoria1 #dj4 ,frog1 injected1 #acf2 to show circulation of blood1 #adj4 ,frog-bit1 rotation in1 #add4 ,fruit-stones1 sections of1 #ajd4 ,fungi1 #ec1 #id4 ,gastric teeth of insects1 #abj2 of molluscs1 #aag4 ,gelatine for injection1 #abd2 preservative liquid1 #hd4 ,glass slides1 #a2 thin1 #c2 thin1 to cut1 #c2 thin1 to measure1 #d2 thin1 to clean1 #e2 cells1 to make1 #hh2 rings for cells1 #hh2 tubes1 #aj4 ,glycerine1 #hd1 #id2 jelly1 #hd1 #ia4 ,goadby's fluid1 #he4 ,gold-size1 #ae4 ,grasses1 #hj4 ,grasshopper1 gizzard of1 #abj4 ,guano1 containing ,diatomace1 #ci4 ,gum-water1 and modifications of1 #ag4 ,gutta-percha cells1 #g2 for liquids1 #hg4 ,hairs1 vegetable1 #df2 to mount dry1 #ed2 to mount as polarizing objects1 #gi2 sections of1 #aje4 ,hepworth1 ,mr41 on mounting insects1 #fh4 ,horn1 sections of1 #ajd4 ,hot-water bath1 use of1 #eh4 ,infusoria1 in preservative liquid1 #ib2 fossil1 #dj4 ,injections1 vi41 #abb2 apparatus for1 #abb2 colours for1 #abe2 directions for1 #abg2 with various colours1 #aca2 mounting of1 #aca2 transparent1 #acc1 #ach4 ,insects1 scales of1 #dh2 to mount1 #di2 legs and feet of1 #ed1 #gb2 eyes of1 #ed1 #gj2 ,mr4 ,hepworth on mounting1 #fh2 antenn of1 #ga2 mouth of1 #gb2 trache and spiracles of1 #gb1 #aae2 parasitic1 #gc2 in preservative liquid1 #id2 eggs of1 #id2 gizzard of1 #abj2 circulation of blood in1 #adb4 ,intestines1 injected1 #acf4 ,knives for dissecting1 #aab2 ,valentin's1 #ajh4 ,labelling of objects1 #ai4 ,lamps1 for mounting1 #ab4 ,larv1 skins of1 #ej4 ,leaves1 sections of1 #ajg2 scales of1 #df1 #ha4 ,liquid-glue1 #af4 ,lungs of animals injected1 #acg4 ,mallow1 pollen of1 #dg4 ,marine glue1 #ae1 #hh4 ,microscope for dissection1 #aaa4 ,miscellaneous1 vii41 #adj4 ,mites1 #gc4 ,molluscs1 tongues of1 #aaf4 ,mosses1 #ea2 in preservative fluids1 #ia4 ,mould 7see ,fungi74 ,mounting objects1 apparatus for1 i42 dry1 ii41 #bb2 in ,canada balsam1 iii41 #ef2 in cells1 iv41 #hc4 ,mouse1 ear of1 #aad2 circulation of blood in1 #adb4 ,mouth of insects1 #gb4 ,muscle1 dissection of1 #aad4 ,needles1 how to mount1 #aj2 for dissection1 #aab2 curved1 for injection1 #abc4 ,nervous tissue1 dissection of1 #aae4 ,nettle leaf1 #eb4 ,newts1 injected1 #acf4 ,onion1 raphides of1 #eb4 ,orbitolite1 section of1 #ig4 ,oxalurate of ammonia1 crystals of1 #ge4 ,palates of ,molluscs 7see tongues74 ,papers1 ornamental1 to cover slides1 #h1 #bg4 ,photographs1 microscopic1 to produce1 #adg2 ,mr4 ,shadbolt on1 #adi4 ,pipes for injecting syringe1 #abb4 ,podura1 scales of1 #di4 ,polariscope1 objects for1 #gd-hb1 #ajd4 ,pollen1 #dg1 #gd4 ,polycystina1 preparation and mounting of1 #fc4 ,preservative liquids1 iv41 #hc2 cells suited for1 #hg-hi4 ,prussian blue for injection1 #acd4 ,raphides1 vegetable1 #eb1 #hj4 ,rhinoceros1 horn of1 #ajd4 ,rhubarb1 spiral vessels of1 #aac4 ,rings and cross of crystals1 #aji4 ,rotation of fluid in cells of plants1 #adc-ade4 ,rush1 section of1 #ajh4 ,rylands1 ,mr4 ,t4 ,g41 on ,diatomace1 #cc1 #ic4 ,salicine1 crystals of1 #gf4 ,saw of watch-spring1 #ig4 ,scales of fishes1 #ec1 #gh2 of leaves1 #df1 #ha2 of insects1 #dh4 ,scissors1 #aj2 for dissection1 #aab4 ,sea-mats1 #ec4 ,sea-soundings1 to cleanse1 #db4 ,sealing-wax varnish1 #ag4 ,sections1 #if2 of shells1 #ig2 of orbitolite1 #ig2 of spines of ,echinodermata1 #ii2 of corals1 #ii2 of coal1 #ii2 of flint1 #aja2 of teeth1 #aja2 of bone1 #ajb2 of fruit-stones1 #ajd2 of horn1 #ajd2 of whalebone1 #aje2 of hairs1 #aje2 of wood1 #ajf2 of leaves1 #ajg2 of sponges1 #ajh2 of skin1 #aji2 of crystals1 #aji2 of seeds1 #aaa4 ,seeds1 #dg1 #gd2 sections of1 #aaa2 growth of1 #ade4 ,shadbolt's turntable1 #i4 ,shells1 sections of1 #ig2 decalcifying1 #ih2 lamin of1 #ih4 ,siliceous cuticles1 #hj4 ,size for injection1 #abd4 ,skins of larv1 #ej2 sections of1 #aji2 sole1 #ed4 ,slides1 glass1 for mounting objects1 #a2 glass1 to clean1 #b2 wood1 c41 #f2 most useful1 #h2 to cover and varnish1 #bg4 ,spicula1 from sponges1 c41 #fg4 ,spines of ,echinus1 #ii4 ,spiracles of insects1 #gb1 #aaf4 ,spiral vessels of vegetables1 #aac4 ,split bristles1 use of1 #aj4 ,sponges1 sections of1 #ajh4 ,spores of ferns1 development of1 #ade2 equisetum1 #adf4 ,starch1 preparation and mounting of1 #gi4 ,sulphate of copper and magnesia1 crystals of1 #gf4 ,syringe for ,canada balsam1 #ei2 for dissection1 #aac2 for injection1 #abb4 ,tadpole1 to show circulation of blood of1 #ada4 ,teeth1 sections of1 #aja4 ,thin glass1 to cut1 #c2 to measure thickness of1 #d2 to clean1 #e4 ,thwaites' preservative liquid1 #he4 ,ticks1 #gc4 ,tissues1 animal and vegetable 7see ,dissection74 ,tongues or palates of ,molluscs1 #aaf4 ,trache of insects1 #gb1 #aae4 ,transfer of objects1 #aj4 ,trough for dissection1 #aac4 ,tubes1 glass1 #aj4 ,turnbull's1 ,dr41 ,prussian blue for injection1 #acd4 ,turpentine1 use of1 #eg4 ,universal stand1 to make1 #bj4 ,valentin's knife1 #ajh4 ,vallisneria spiralis1 rotation in1 #adc2 to cultivate1 #add4 ,varnishes1 #ag4 ,vegetable objects1 to mount dry1 #df2 to mount in jelly1 #ia2 dissection of1 #aac4 ,watch-glasses1 #ab4 ,whalebone1 sections of1 #aje4 ,wood1 sections of1 #ajf4 ,zoophytes1 to mount dry1 #ec2 ,dr4 ,golding ,bird on mounting1 in balsam1 #fe2 as polarizing objects1 #gi4 ,,cox ,,and ,,wyman1 ,,printers1 ,,great ,,queen ,,street1 ,,london4 ,transcriber's ,notes ,punctuation and spelling were made consistent when a predominant preference was found in the original book2 otherwise they were not changed4 ,inconsistent hyphenation was not changed4 ,simple typographical errors were corrected2 unbalanced quotation marks were remedied when the change was obvious1 and otherwise left unbalanced4 ,the ,table of ,contents was added by the ,transcriber4 ,the index was not checked for proper alphabetization or correct page references4 ,roman numeral references are to chapters1 not to pages4 ,page #ajf3 ,t indicates a boldface1 sans-serif 8,t04