,,university ,,of ,,cape ,,town4 ,zoological ,department4 ,,dissection ,,of ,the ,platana and the ,frog ,,by ,j4 ,d4 ,f4 ,,gilchrist1 ,m4,a41 ,d4,,sc41 ,,ph4,d41 ,professor of ,zoology in the ,university of ,cape ,town1 ,,and ,c4 ,,von ,,bonde1 ,m4,a41 ,lecturer in ,zoology in the ,university of ,cape ,town4 ,illustration #aiai4 ,,cape ,,times ,,limited1 ,,cape ,,town4 ,,preface ,,and ,,instructions4 ,owing to the fact that some of the types of animals available for the study of ,zoology in ,south ,africa differ from those described in text books for students in other countries1 it has been found necessary to draw up special directions and diagrams for laboratory use in this country4 ,these are now put in the more convenient form of a text book1 which1 though intended primarily for the use of the students of the ,university of ,cape ,town1 may1 it is hoped1 prove useful to others engaged in the teaching and study of ,zoology in ,south ,africa4 ,the general plan of the course intended to be followed is first an introductory study of a type of vertebrate4 ,the ,platana or ,clawed ,toad1 ,xenopus lvis1 is the most convenient type for this in ,south ,africa and in some respects is more instructive than the ,frog4 ,xenopus is therefore chiefly dealt with1 but ,rana can also be used1 the differences in this type being indicated in italics4 ,it is recommended that both types be studied where possible4 ,only these two types are dealt with here1 but may be followed by descriptions of other ,south ,african types1 such as the ,south ,african ,crawfish1 ,dogfish1 ,earthworm1 etc4 ,it is intended that the student should make drawings of his dissections on the blank page4 ,he should not copy the diagrams1 but draw what he actually sees1 and be prepared to demonstrate the parts to the teacher4 ,the instruments required are a large and a small pair of scissors1 a large and a small scalpel1 moderately fine forceps1 a seeker1 and pins4 ,we are indebted to ,mr4 ,w4 von ,bonde1 ,m4,a41 for the drawing of ,figs4 #c-e1 #g-aj4 ,j4 ,d4 ,f4 ,g4 ,c4 v4 ,b4 ,zoological ,laboratory1 ,university of ,cape ,town1 ,june1 #aiai4 ,,the ,,platana 7,xenopus lvis74 ,,the ,,frog 7,rana fuscigula74 ,first ,day4 ,external ,characters4 #a4 ,make a drawing of the animal viewed from above1 showing3-- 7a7 ,the nostrils4 7b7 ,the eyes4 7c7 ,the nictitating membrane and a short tentacle beneath the eye4 ,the tentacle is absent in the ,frog4 7d7 ,the tympanic membrane1 which is not shown in the ,platana1 but is well marked in the ,frog4 7e7 ,the opening of the cloaca4 7f7 ,the limbs and their divisions4 7g7 ,the skin with tube-like lines round the body4 ,in the ,frog these lines are not present4 ,illustration3 ,,fig4 #a4--,xenopus lvis and ,rana fuscigula4 #b4 ,make an enlarged drawing1 about twice the natural size1 showing3-- 7a7 ,the fore-limb with the digits4 7b7 ,the hind-limb with the digits4 ,the inner three digits have claws4 ,the claws are absent in the ,frog4 ,name the parts of these limbs1 and number the digits from within outwards1 noting that the first is absent in the fore-limb4 ,mouth ,cavity4 ,open the mouth cavity widely1 and make a sketch showing3-- 7a7 ,the teeth on the upper jaw4 7b7 ,there are no teeth on the vomer4 ,in the ,frog each vomer is supplied with teeth4 7c7 ,the internal openings of the nostrils4 7d7 ,the single opening of the ,eustachian tubes4 ,in the ,frog there is an opening on each side4 7e7 ,there is no tongue4 ,a tongue is present in the ,frog4 7f7 ,the glottis4 7g7 ,the gullet4 ,owing to the complexity of the ,eustachian tubes and the bony form of the ear cavity1 it is not possible to pass a seeker from the ,eustachian aperture through the tympanic membrane4 ,in the ,frog the ,eustachian tubes are short and straight and permit of this being done4 ,illustration3 ,,fig4 #b4--,mouth cavity of ,xenopus and ,rana4 ,muscular ,system and ,vascular ,system 7,part74 #a4 ,pin the ,platana on its back in water1 and cut through the skin with scissors along the middle line1 throughout the whole length of the body4 ,pin back the skin on each side1 and make a drawing showing3-- 7a7 ,the muscles3 7i7 ,two pectoralis muscles passing from the base of the arm1 the one to the middle line of the body1 and the other over the abdominal region to the posterior part of the body4 ,cut through this latter muscle at its anterior end1 and fold it backwards to expose the underlying brachial vein4 7ii7 ,the rectus-abdominis muscles passing along the mid-ventral line of the body1 with the white line 7linea alba7 in the centre4 7iii7 ,the deltoid muscle to the arm4 7iv7 ,the mylo-hyoid muscle1 on the underside of the mouth region4 7v7 ,the obliquus-externus muscle1 lying under the second pectoralis muscle noted above4 7b7 ,the cutaneous and the muscular veins1 lying under the pectoralis muscle1 and arising independently from the subclavian vein4 ,they supply the skin and muscles in the region of the arm4 ,there is a second cutaneous vein arising from the abdominal vein and extending on to the skin of the abdomen4 ,two other small cutaneous veins are seen on the skin of the leg1 and another on the skin under the mouth4 ,in the ,frog a single musculo-cutaneous vein is seen lying under the pectoralis muscle and extends on to the skin4 7c7 ,the abdominal vein1 partly visible through the wall of the body1 in the centre of the rectus-abdominis muscle4 7d7 ,the brachial vein going to the arm1 near which may often be seen the white brachial nerve4 ,endeavour to trace the point of origin of the brachial1 muscular1 and cutaneous veins 7or the brachial and musculo-cutaneous veins in the ,frog7 as shown in the figures4 ,illustration3 ,,fig4 #c4--,muscular ,system and ,vascular ,system 7part7 of ,xenopus and ,rana4 #b4 ,make an incision in the body wall1 slightly to the right side of the abdominal vein1 which may now be seen clearly on the inner side of the body wall4 ,carefully detach this vein from the abdominal wall4 ,second ,day4 ,skeletal ,system 7,part74 #a4 ,remove the pectoralis muscles covering the body between the arms to show the bones of the central part of the shoulder girdle and sternum1 viz43-- 7a7 ,the thick coracoids4 7b7 ,the more slender clavicles anterior to them1 both extending from the base of the arm on each side towards the centre of the body4 7c7 ,the sternum1 consisting of a median row of cartilages which are believed to be derived from the shoulder girdle4 ,it does not1 therefore1 correspond to1 or is not homologous with1 the sternum of the ,pigeon or the ,rabbit1 which is derived from the ribs4 ,the sternum consists of the following parts3 7i7 ,the two epicoracoids consisting of cartilage4 7ii7 ,the metasternum which is broad and consists of cartilage only4 ,illustration3 ,,fig4 #d4--,pectoral ,girdle of ,xenopus and ,rana4 ,in the ,frog the sternum is composed of the following parts3-- 7i7 ,the omosternum consisting of two parts1 an anterior cartilaginous part 7sometimes called the omosternum7 and a posterior bony part 7sometimes called the episternum74 7ii7 ,the two epicoracoids consisting of cartilage4 7iii7 ,the metasternum consisting of two parts1 an anterior bony part 7sometimes called the sternum7 and a posterior cartilaginous part 7sometimes called the xiphisternum74 ,make a sketch of the pectoral girdle4 #b4 ,cut through the coracoids and clavicles on each side1 close to the base of the arm1 and carefully remove this part of the pectoral girdle and sternum so as to show the heart lying underneath4 ,illustration3 ,,fig4 #e4--;,dissection of ,xenopus and ,rana to show the ,alimentary ,system1 etc4 ,alimentary ,system4 ,make a sketch showing3--,the heart1 lungs1 liver1 gall bladder and bile duct going to the duodenum1 exposed parts of the stomach1 duodenum1 small intestine 7or ileum71 large intestine1 urinary bladder1 pancreas1 and spleen4 ,third ,day4 ,vascular ,system 7continued74 ,a4 ,venous ,system4 #a4 ,note3-- 7a7 ,the heart lying in the thin pericardium1 the two auricles1 the single ventricle1 the truncus arteriosus which divides into two branches4 ,remove the pericardium from the heart1 and tilt the apex of the heart forwards1 noting the sinus venosus into which the right and the left superior ven cav 7or precavals7 and the single inferior vena cava 7or postcaval7 open4 7b7 ,the veins passing from each side of the sinus venosus4 ,each superior vena cava is joined by the following branches3-- 7i7 ,the external jugular vein from the region of the tongue and the mandible4 7ii7 ,the internal jugular vein from the head and a thick subscapular vein from the shoulder4 ,these veins join the superior vena cava independently of each other so that there is no innominate vein as in the ,frog4 7iii7 ,the subclavian vein1 made up of a brachial vein from the arm1 a cutaneous vein from the skin1 and a muscular vein from the abdominal muscles4 ,the cutaneous and the muscular veins are separate veins so that there is no single musculo-cutaneous vein4 ,in the ,frog the superior vena cava is joined by the following branches3-- 7i7 ,the external jugular vein1 formed by the union of a lingual vein from the tongue and a mandibular vein from the margin of the lower jaw4 7ii7 ,the internal jugular vein from the head and the subscapular vein from the back of the arm and shoulder1 both joining the superior vena cava by a common vein1 the innominate4 7iii7 ,the subclavian vein1 formed by the brachial vein from the fore-limb and a musculo-cutaneous vein from the muscles of the body and from the skin4 7c7 ,the hypoglossal and the glossopharyngeal nerves1 both running alongside of the lingual artery4 ,make an enlarged drawing showing the above parts 7a7 and 7b74 #b4 ,note the inferior vena cava1 receiving the renal veins from the kidneys1 the hepatic veins from the liver1 and opening into the sinus venosus4 #c4 ,trace back the abdominal vein1 and note that it is formed by the union of the two pelvic veins1 which pass along the bases of the legs4 ,the pelvic veins occur deep down in the body under the posterior part of the pelvic girdle1 which should be cut through in order to see them4 ,at the union of the pelvic veins to form the abdominal vein a small rectal vein1 passing along the ventral surface of the rectum1 joins the abdominal vein4 ,in order to make out the femoral and the sciatic veins1 turn the ,platana over and remove the skin from the back of the leg4 ,the femoral vein may then be seen lying on the surface of the leg1 between two of the muscles4 ,by carefully separating these muscles the whole of the femoral vein may be exposed4 ,deeper down in the muscles of the leg lies the sciatic vein1 and1 between the sciatic and the femoral veins1 the internal iliac artery may be seen running alongside of the sciatic nerve4 ,trace the femoral and the sciatic veins forward1 and note that they join together at the point where they meet the pelvic veins and then run forward to the kidney as the renal portal vein on each side4 ,turn the ,platana over again on to its back and note the renal portal vein from the ventral side4 ,joining the renal portal vein is a large vein formed of two branches4 ,the one branch arises in the abdominal wall1 while the other passes along the base of the leg and joins the abdominal vein4 ,on each side three dorso-lumbar veins join the renal portal vein4 ,illustration3 ,,fig4 #f4--,venous ,system of ,xenopus and ,rana4 ,in the ,frog the abdominal vein is also formed by the union of the two pelvic veins4 ,the pelvic veins1 however1 lie more superficially than in the ,platana4 ,the femoral vein which passes along the front of the thigh divides into two branches1 the one branch forming the pelvic vein1 the other1 joined by the sciatic vein from the muscles and skin of the back of the thigh1 forming the renal portal vein extending along the outer side of the kidney4 ,the dorso-lumbar vein from the dorsal wall of the body joins the renal portal vein4 ,make a drawing showing the above parts4 ,b4 ,arterial ,system4 ,distend the sophagus with a piece of cotton wool or paper to show the blood vessels more clearly4 ,trace out the anterior part of the arterial system1 made up of two branches of the truncus arteriosus each of which divides into3-- 7a7 ,the carotid arch passing to the head region4 7b7 ,the systemic arch curving round the sophagus4 7c7 ,the pulmo-cutaneous arch to the lungs and the skin4 ,fourth day4 ,arterial ,system 7continued74 #a4 ,trace the carotid arch1 which gives off3 7a7 ,two lingual arteries having a common point of origin near the carotid gland4 7b7 ,a carotid artery passing to the head4 ,at its origin it is slightly swollen into the carotid gland4 #b4 ,trace the systemic arches which run backwards on each side of the body1 meeting posteriorly to form the dorsal aorta4 ,each systemic arch gives rise to an artery which branches into3-- 7i7 ,a scapular artery to the pectoral girdle4 7ii7 ,a cutaneous artery to the skin4 7iii7 ,a brachial artery to the arm4 ,trace the dorsal aorta backwards1 and note that it gives rise to the cliaco-mesenteric artery about midway between its origin and the origin of the first pair of renal arteries4 ,the dorsal aorta then passes between the kidneys giving four renal arteries to each1 and proceeds backwards and divides into an internal iliac artery to each leg4 ,this artery lies between the femoral and the sciatic veins4 ,from each of these arteries a branch is given off which divides into3 7i7 ,an iliac artery to the muscles around the ilium4 7ii7 ,a cutaneous artery to the skin of the body1 just anterior to the leg4 7iii7 ,a small artery to the anterior dorsal surface of the hind limb4 #c4 ,trace the pulmo-cutaneous arch1 which gives off3-- 7a7 ,a pulmonary artery1 running along the outer side of the whole length of the lung4 7b7 ,a cutaneous artery1 which at first runs forwards to the base of the arm1 and becomes spread out on the skin of the back of the head4 ,in the ,frog #a4 ,the carotid arch gives off3-- 7a7 ,a lingual artery supplying the tongue4 7b7 ,a carotid artery1 running round the side of the sophagus1 and supplying the head4 ,at its origin it is slightly swollen into the carotid gland4 #b4 ,the systemic arches run backwards on each side of the body1 and meet posteriorly to form the dorsal aorta4 ,each systemic arch gives off3-- 7a7 ,a subclavian artery to the shoulder and fore-limb4 7b7 ,an occipito-vertebral artery to the head and the vertebral column4 7c7 ,an sophageal artery to the dorsal wall of the sophagus4 7d7 ,a laryngeal artery to the larynx4 ,at the point where the dorsal aorta is formed1 note the origin of the cliaco-mesenteric artery which sends branches to the stomach1 liver1 intestine1 and spleen4 ,trace the dorsal aorta backwards and note that it passes between the kidneys1 to each of which it gives off four renal arteries and then it divides posteriorly into an iliac artery to each leg4 ,the iliac artery is continued backwards as the femoral artery in the leg4 #c4 ,the pulmo-cutaneous arch gives off3-- 7a7 ,a pulmonary artery1 running along the outer side of the whole length of the lung4 7b7 ,a cutaneous artery1 which at first runs forwards and upwards1 and then turns backwards1 supplying the skin of the back and the sides of the head4 ,make a complete sketch of the arterial system4 ,illustration3 ,,fig4 #g4--;,arterial ,system of ,xenopus and ,rana4 ,cut out the heart1 leaving attached to it as much as possible of the large vessels4 ,note the sinus venosus1 truncus arteriosus1 auricles1 and ventricle4 ,open the auricles and observe the division between them and the openings of the veins passing into them4 ,make a section through the auricles and ventricle noting the thick muscular walls of the ventricle and the valves between it and the auricles4 ,respiratory ,system and ,alimentary ,system 7continued74 #a4 ,remove the mylo-hyoid muscles to expose the hyoid apparatus4 ,pass a seeker through the glottis to one of the lungs and slit it open with a pair of scissors4 ,examine the structure of the lung4 #b4 ,remove the whole of the alimentary canal with the lungs1 liver1 pancreas1 and spleen1 by cutting through the sophagus and the large intestine before it joins the cloaca1 and detaching it from the roof of the body cavity without injuring the kidneys and the reproductive organs4 ,draw the complete alimentary canal4 ,illustration3 ,,fig4 #h4--;,alimentary ,canal of ,xenopus and ,rana4 ,urinogenital ,system4 ,note the kidneys1 two elongated1 flattened1 dark-red bodies lying one on each side of the vertebral column towards the posterior end of the abdominal cavity4 ,from the outer edge of each kidney a ureter arises and runs backward1 opening into the cloaca on the dorsal side1 opposite the opening of the urinary bladder4 ,in the ,frog the adrenal bodies may be seen on the ventral sides of the kidneys as small yellow patches4 ,in the male ,platana note3-- 7a7 ,the testes1 a pair of ovoid pale-yellow bodies attached to the dorsal wall of the body cavity by a fold of the peritoneum4 ,they lie on the ventral sides of the kidneys and are connected to them by efferent vessels which pass into the kidneys4 7b7 ,the corpora adiposa or fatty bodies lying in front of the kidneys4 7c7 ,the ureters which run along the outside of the kidneys and unite posteriorly to form a single duct opening into the cloaca4 ,in the ,frog the ureters do not join together but open separately into the cloaca4 ,each ureter has a slight swelling1 the vesicula seminalis1 on its outer side4 ,illustration3 ,,fig4 #i--,male ,urinogenital ,system of ,xenopus and ,rana4 ,in the female ,platana note3-- 7a7 ,the ovaries1 a pair of irregularly-lobed organs usually consisting of a mass of rounded black and white bodies1 the ova4 ,the ovaries are attached to the dorsal wall of the body cavity by a fold of the peritoneum4 7b7 ,the corpora adiposa lying in front of the kidneys4 7c7 ,the long convoluted oviducts opening into the body cavity in front and into the cloaca behind4 ,the ureters open separately into the cloaca in the female4 ,make a drawing of the urinogenital system4 ,illustration3 ,,fig4 #aj4--;,female ,urinogenital ,system of ,xenopus and ,rana4 ,fifth ,day4 ,skeletal ,system 7continued74 ,a4 ,the ,pectoral and ,pelvic ,girdles and ,limbs4 #a4 ,detach a fore-limb with the remaining parts of the pectoral girdle4 ,make a preparation showing these various parts3-- ,supra-scapula1 scapula1 remainders of the clavicle and the coracoid1 humerus1 radio-ulna1 carpal bones1 and digits4 ,draw these parts4 ,illustration3 ,,fig4 #aa4--,pectoral ,girdle of ,xenopus and ,rana4 #b4 ,detach the pelvic girdle from the transverse processes of the #ith vertebra4 ,remove it with the hind-limbs from the body4 ,detach the femur from one side of the pelvic girdle1 and make a sketch showing the following parts of the pelvic girdle3--,acetabulum1 ilium1 ischium1 and pubis4 ,illustration3 ,,fig4 #ab4--,pelvic ,girdle of ,xenopus and ,rana4 ,make a preparation and a sketch showing the femur1 tibia-fibula1 astragalus1 calcaneum and the other bones of the tarsal region1 five metatarsals1 and digits4 ,number the digits from the inner side4 ,illustration3 ,,fig4 #ac4--;,hind and ,fore ,limbs of ,xenopus4 ,b4 ,the ,vertebral ,column4 #a4 ,remove the skin and muscles from the dorsal surface of the back to show the nine vertebr and the urostyle4 ,make a drawing showing the vertebr with their transverse processes1 and the urostyle attached to the posterior end of the #ith vertebra4 ,illustration3 ,,fig4 #ad4--,vertebral ,column of ,xenopus and ,rana4 ,the #bnd1 #crd and #dth vertebr bear long transverse processes curved backwards1 those of the #crd and #dth being tipped with small cartilaginous ribs4 ,the transverse processes of the #eth1 #fth1 #gth and #hth vertebr are slender and project forwards and outwards4 ,the #ith vertebra has long flat wing-like processes attached to which are the ilia of the pelvic girdle4 ,the urostyle is fused to the #ith vertebra4 ,in the ,frog the transverse processes are produced outwards and they do not bear cartilaginous ribs4 ,the urostyle is attached to the #ith vertebra by two facets4 ,note the intervertebral foramina for the exit of the nerves from the spinal cord1 and the intervertebral discs4 #b4 ,remove1 examine1 and draw the #ast or atlas vertebra1 note its ring-like form1 absence of transverse processes1 the concave facets by which it articulates with the two occipital condyles of the skull4 #c4 ,remove1 examine1 and draw the #crd vertebra and note the opisthoclous centrum1 neural arch and neural spine1 anterior and posterior zygapophyses1 the transverse processes1 and the cartilaginous ribs4 ,the centrum is proclous in the ,frog and there are no ribs4 #d4 ,remove and examine the #hth vertebra and note that the centrum is opisthoclous4 ,make a drawing of a section showing the centrum4 ,in the ,frog the centrum is amphiclous4 #e4 ,remove and examine the #ith vertebra or sacrum1 and note that the centrum is slightly convex on the anterior surface4 ,the urostyle is fused to the posterior surface of the #ith vertebra4 ,note also the long flat wing-like transverse processes4 ,in the ,frog the centrum is also convex anteriorly and on the posterior surface there are two convex facets for the articulation of the urostyle4 ,sixth ,day4 ,skeletal ,system 7continued74 ,c4 ,the ,skull4 #a4 ,remove the skin and other tissues from the top of the skull and observe the large fronto-parietals1 nasals1 supra-ethmoid1 premaxill1 maxill1 squamosals1 exoccipitals1 and pro-otics4 ,the quadrato-jugals are very inconspicuous4 ,the extrastapedial plate of cartilage is well marked and the bony columella may be seen lying underneath it4 ,the sides of the skull are ossified and may represent the orbitosphenoids and alisphenoids of higher types4 ,the supra-occipital consists of a piece of cartilage4 ,illustration3 ,,fig4 #ae4--;,dorsal view of ,skull of ,xenopus and ,rana4 ,in the ,frog there is no supra-ethmoid present1 but a sphenethmoid closes the front of the cranial cavity4 ,the sides of the skull are cartilaginous4 ,a quadrato-jugal is well marked1 but the quadrate consists of a piece of cartilage at the posterior end of the quadrato-jugal between the pterygoid and the squamosal4 ,the lower jaw articulates with it4 ,the columella is usually not well shown4 ,make a drawing of the dorsal side of the skull4 #b4 ,remove the skin from the roof of the mouth and note the parasphenoid and single vomer1 pterygoids1 which are large and send leaf-like processes towards the middle line covering the ,eustachian passages1 squamosals1 quadrates1 basi-occipital1 ex-occipitals1 premaxill1 and maxill4 ,the orbitosphenoid and alisphenoid are well marked4 ,there are no palatines present4 ,illustration3 ,,fig4 #af4--,ventral view of ,skull of ,xenopus and ,rana4 ,in the ,frog there are a pair of vomers bearing the vomerine teeth1 palatines1 and quadrato-jugals4 ,the pro-otics1 which are not seen in a ventral view of the skull in the ,platana1 being covered over by the pterygoids1 are shown in the ,frog4 ,make a drawing of the ventral side of the skull4 ,illustration3 ,,fig4 #ag4--,side view of ,skull of ,xenopus and ,rana4 #c4 ,make a drawing of the bones of the skull viewed from the posterior end1 showing the occipital condyle at each side of the foramen magnum1 ex-occipitals1 basi-occipital1 supra-occipital1 pro-otics1 columella1 and quadrate4 ,in the ,frog the basi-occipital and supra-occipital are not developed4 #d4 ,remove the skin from the lower jaw and make out the bones surrounding the original ,meckel's cartilage1 viz41 the mento-meckelian1 dentary1 and articular4 ,in the ,frog the lower jaw is composed of the mento-meckelian1 dentary and angulo-splenial4 ,make a drawing of the lower jaw4 ,nervous ,system4 ,a4 ,the ,central ,nervous ,system4 ,the ,brain4 ,carefully remove the fronto-parietals so as to expose the brain1 and note the following parts3-- 7a7 ,the olfactory lobes1 forming the most anterior portion of the brain1 united together in the middle line4 ,anteriorly the olfactory nerves are given off4 7b7 ,the cerebral hemispheres1 a pair of smooth elongated bodies4 7c7 ,the thalamencephalon1 lying immediately behind the cerebral hemispheres4 ,it is covered by the choroid plexus1 a thick vascular membrane1 and gives rise dorsally to the stalk of the pineal body4 7d7 ,the optic lobes1 a pair of oval bodies4 7e7 ,the cerebellum1 a narrow transverse band immediately behind the optic lobes4 7f7 ,the medulla oblongata behind the cerebellum4 ,it gradually tapers towards its posterior end1 where it is continuous with the spinal cord4 ,on its roof the pia mater forms a very vascular choroid plexus4 ,make a sketch of the brain4 ,seventh ,day4 7,revision47 ,with a second specimen revise the second1 third1 and fourth days' work1 paying particular attention to the vascular system4 ,eighth ,day4 ,nervous ,system 7continued74 ,b4 ,the ,peripheral ,nervous ,system4 #a4 ,the ,spinal ,nerves4 ,remove the abdominal viscera carefully so as to expose the spinal nerves which are seen as white cords on each side of the vertebral column as follows3-- 7a7 ,the first or hypoglossal nerve arising between the #ast and #bnd vertebr4 ,it runs forwards on the under surface of the head beneath the mylo-hyoid muscle and supplies the tongue4 ,it was noted in the third day's work4 7b7 ,the second and third nerves unite immediately after escaping from the spinal cord to form the brachial plexus1 which supplies the muscles of the shoulder1 and then extends along the arm4 7c7 ,the fourth1 fifth1 and sixth nerves are small and supply the muscles and the skin of the body wall4 7d7 ,the seventh1 eighth1 and ninth nerves run obliquely backwards1 the eighth and ninth uniting to form the sciatic plexus1 which gives rise to the large sciatic nerve which extends along the thigh1 and down the leg4 ,the sciatic plexus also receives a branch from the seventh nerve4 7e7 ,the tenth or coccygeal nerve1 which escapes through a small aperture in the side of the urostyle1 and is distributed to the walls of the cloaca and urinary bladder4 ,it is connected by a branch with the sciatic nerve4 ,this nerve is frequently small or absent in the ,platana4 ,in the ,frog1 the seventh1 eighth1 and ninth nerves unite to form the sciatic plexus which gives rise to the large sciatic nerve extending along the thigh1 and dividing above the knee into the tibial and peroneal nerves to the leg and the foot4 ,the tenth nerve is present4 #b4 ,the ,sympathetic ,nervous ,system4 ,this system consists of a cord on each side closely following the course of the systemic arches and the dorsal aorta4 ,it has on it six ganglionic swellings1 and there are connections between the ganglia and all the spinal nerves4 ,anteriorly each of the cords is joined to the vagus nerve2 it ends posteriorly as a broad swelling on the ninth spinal nerve4 ,in the ,frog the system consists of a chain of ganglia on each side of the body closely following the course of the systemic arches and the dorsal aorta4 ,the cords have connections with the spinal nerves4 ,anteriorly each cord ends in the ,gasserian ganglion of the trigeminal nerve and posteriorly it is united with the coccygeal nerve by a varying number of branches4 ,make a complete sketch showing the spinal nerves and the sympathetic nervous system4 #c4 ,the ,cranial ,nerves4 ,expose the brain and note the following cranial nerves3-- 7a7 ,the olfactory nerve1 arising from the anterior end of the olfactory lobes1 supplying the olfactory capsule4 7b7 ,the optic nerve1 arising from the ventral surface of the brain below the optic lobes1 supplying the retina of the eye4 7c7 ,the trigeminal nerve1 arising just behind the optic nerve1 giving rise to the following branches3-- 7i7 ,the ophthalmic nerve1 which passes over the muscles of the eye and supplies the skin in the region of the olfactory capsule4 7ii7 ,the maxillary nerve1 which runs forward under the eyeball1 and supplies the skin covering the upper jaw4 7iii7 ,the mandibular nerve1 which is at first continuous with the maxillary1 and then bends round the inner surface of the upper jaw to extend along the outer surface of the mandible4 7d7 ,the glossopharyngeal and the vagus 7or pneumogastric7 nerves1 leaving the skull together1 immediately behind the auditory capsule4 ,the glossopharyngeal passes along in front of the hypoglossal nerve and proceeds along the base of the tongue4 ,the vagus1 after giving off branches to the dorsal muscles1 reaches the walls of the pharynx and run obliquely backwards to supply the pharynx1 heart1 lungs and stomach4 ,illustration3 ,,fig4 #ah4--;,brain4 ,cranial ,nerves1 ,spinal ,nerves1 and ,sympathetic ,nervous ,system of ,xenopus and ,rana4 ,make a complete sketch showing the brain and the above-mentioned cranial nerves4 99 99 99 99 99 ,transcriber's ,notes3 ,every effort has been made to replicate this text as faithfully as possible1 including inconsistencies in formatting4 ,italic text is denoted by underscores and bold text by equal signs4 ,both exoccipitals and ex-occipitals occur in original text1 left as printed4