,transcriber's ,note3 ,this book uses   
the convention that items printed in    
the original text in italics are        
surrounded by underscores like this  and
 that items printed for emphasis in     
small-caps are rendered in all  caps4   
,,experiments                           
,,and                                   
,,observations                          
,,relative ,,to ,,the                   
,,influence ,,lately ,,discovered ,,by  
,m4 ,,galvani1                          
,,and ,,commonly ,,called               
,,animal ,,electricity4                 
,,by ,,richard ,,fowler4                
,,edinburgh3                  ,,printed 
,,for ,t4 ,,duncan1 ,p4 ,,hill1         
,,robertson                     ,,berry1
 ,,and ,g4 ,,mudie2 ,,and ,j4 ,,johnson 
,,st ,,paul's ,,church-,,yard1 ,,london4
                                        
#agic4                                  
----------------------------------------
--------------------------------        
,,preface4      ,the subject of the     

following experiments1 has excited such 
general  curiosity1 that every new fact 
respecting it1 may afford some          
gratification2 and although the few     
which ,i have to offer1 have not led  me
 to what many may think very important  
conclusions1 they will not ,i  hope be  
found wholly undeserving of attention4  
,the experiments were  begun1 with the  
view of ascertaining if the influence   
discovered by ,m4  ,galvani1 be         
referrible to any known law of nature1  
or if it be itself a  new law4          
,finding that it indicated1 with        
tolerable accuracy1 the presence of     
very small degrees of the contractile   
power of muscles1 without  appearing in 
the least to diminish that power1 as    
electricity and most  other stimuli     
never fail to do2 ,i thought it might be
 used with  advantage1 as a test1 in the
 investigation of some important        
subjects  in physiology2 and ,i have    
accordingly employed it as such4        
,every circumstance1 observed in the    

course of these experiments1 was        
carefully noted down1 at the instant it 
occurred1 and the greater  number of    
these was made in the presence of       
gentlemen1 whose accuracy ,i  had reason
 to hope would detect any fallacy1 which
 might have escaped  myself4 ,i have a  
particular pleasure1 in expressing my   
obligation to ,mr  ,george ,hunter of   
,york1 for the very friendly assistance 
which he  afforded me1 in almost every  
experiment1 which rendered such         
assistance  necessary4     ,edin4 ,may  
#bh4          #agic4                    
----------------------------------------
--------------------------------        
,,section ,i4                ,are the   
,phenomena1 exhibited by the            
,application                        of  
certain different ,metals               
to ,animals1 referrible to ,electricity8
      ,the whole train of circumstances1
 which preceded this discovery1 had a   
tendency to occasion the belief of its  
relation to electricity4    ,some       

accidental appearances1 certainly       
electrical1 excited1 by their  novelty1 
the attention of the ,professor of      
,anatomy at ,bologna1 to the            
investigation of the possible1 but      
unknown1 dependencies of the motions  of
 animals upon electricity2 and the      
astonishing effects of that  influence  
upon the human body1 particularly in    
paralytic diseases1  whether owing to   
derangements of the nerves1 or of the   
muscles2 the  experiments1 which prove  
that the fluids of animals are better   
conductors of electricity1 than water   
is2 and that1 8if an electric  shock    
pass through a given part of a living   
animal1 the same shock1  after the      
animal is dead1 will be visibly         
transmitted over the surface  of the    
part1 but not through it#a30 the        
recollection1 too1 of that  singular    
power1 which some animals possess1 as   
the torpedo1 the  gymnotus electricus1  
and the silurus electricus1 of          
collecting and  discharging at pleasure 

the electrical fluid2 but1 above all1   
the  wonderful1 but solitary1 instance  
of an electrical shock received from  a 
mouse1 under dissection1 recently       
related by his countryman ,cotugno2     
were circumstances1 which seem to have  
rendered the expectations of the        
,professor not a little sanguine as to  
his success4    ,at length1 after many  
ingenious and interesting experiments1  
illustrative of the relations which     
subsist between artificial  electricity 
and the involuntary motions of animals1 
a happy accident  discovered to him the 
phenomena1 which have since been the    
objects of  so much curious research1   
and which have given to immortality the 
name  of ,galvani4    ,he one day       
observed1 that some frogs1 hooked by the
 spine of the back1  and suspended from 
the iron palisades1 which surrounded his
 garden1  contracted frequently and     
involuntarily4 ,examining minutely into 
the  cause of these contractions1 he    
found that he could produce them at     

pleasure1 by touching the animals with  
two different metals1 at the  same time 
in contact with each other4    ,to a    
mind prepared by such observations and  
experiments as those which  had         
previously occupied ,m4 ,galvani1 the   
resemblance which this new  discovery   
bore to the facts he had before         
observed1 must have produced  conviction
 of the identity of their cause2 and the
 experiments1 which  have since been    
made both by himself1 and ,dr ,valli1   
have given no small  degree of          
plausibility to the opinion4 ,a         
repetition of some of these  experiments
 excited my doubts as to the legitimacy 
of the conclusions  which had been drawn
 from them1 and induced me at length to 
proceed in  the following investigation4
    ,my first object was to ascertain as
 well the various circumstances1  which 
are essentially requisite to the        
production of these new  phenomena1 as  
those in which they can be rendered most
 obvious4 ,after a  great variety of    

experiments1 of which it would be       
unnecessary here to  relate more than   
the result1 ,i found that ,i could not  
excite in an  animal the appearances    
described by ,galvani with any          
substances  whatever1 whether solid or  
fluid1 except the metals3 and that the  
mutual contact of two different metals  
with each other1 so far as ,i was  able 
to determine1 was in every case         
necessary to the effect4    ,when metals
 are either calcined1 or combined with  
acids1 they are no  longer capable of   
exciting contraction4 ,in estimating the
 comparative  powers of different metals
 as excitors1 ,i found zinc#b by far the
 most  efficacious1 especially when in  
contact with gold1 silver1 molybdena1   
steel1 or copper1 although these latter 
excite but feeble contractions  when in 
contact only with each other4 ,next to  
zinc1 tin foil1 and lead  appear to be  
the best excitors4 ,but with zinc1 and  
gold1 silver1 or  molybdena1 ,i have    
frequently succeeded in exciting        

contractions in the  foot of a frog1    
upwards of a day after they had ceased  
to be excited1  by arming the nerve with
 tin foil1 and using some other metal as
 a  conductor1 in the way the experiment
 is commonly performed4    ,when the    
bulk of the metals is large1 and the    
quantity of surface1 of  an animal with 
which they are in contact1 is           
considerable1 ,i think1 the             
contractions are both stronger and more 
readily excited1 than when the  reverse 
of this is the case4 ,thus ,i have      
almost always been able to  make a limb 
contract1 by laying it upon a broad     
plate of zinc1 and  employing a half    
crown piece for an excitor1 long after a
 small piece  of zinc1 and a silver     
probe1 had failed to produce any effect4
    ,i have said1 that1 in order to     
excite contractions1 ,i believe it      
necessary that two different metals1    
communicating with the part to be       
excited1 should be in contact with each 
other4 ,some few instances have  been   

observed1 which seem to prove the       
contrary4 ,in a lecture1 so long  ago as
 ,october last1 in which ,dr ,baillie of
 ,london mentioned ,galvani's           
discovery1 ,i think ,i remember him     
saying1 that he had twice or thrice     
produced contractions by the application
 of one metal only3 and ,dr  ,valli1 in 
his #ith letter upon this subject1      
speaks of his having done  the same with
 a pair of scissars1 made of bad steel1 
and in a frog  recently killed4 ,i think
 it not impossible that there may have  
been  some unnoticed fallacy in these   
instances4 ,i happened one day to touch 
the crural nerve of a frog1 with a small
 gold tooth-pick slid from a  silver    
case1 and the leg instantly contracted2 
,i again touched it1 and  it again      
contracted4 ,at another time ,i observed
 contractions from  touching a nerve1   
with a silver cannula1 and at another   
from placing  one in the folds of a     
silver chain4 ,all these appeared at the
 time to  be so many decisive instances 

of contractions from the application of 
one metal1 till the following experiment
 seemed to afford a different           
explanation4 ,having placed1 one end of 
a silver probe upon the sciatic  nerve  
of a frog1 lying in water some inches   
below the surface1 ,i  observed that no 
contractions followed1 neither did they1
 when ,i  touched the part of the probe 
above the surface with a piece of zinc4 
,but when ,i touched it at the surface1 
so that both the zinc and the  silver   
were in contact with the water1 although
 the zinc was at the  same time many    
inches removed from the frog1           
contractions were produced  equally     
vigorous1 as if both the metals had been
 in immediate contact  with the frog4   
,i was now no longer at a loss to       
account for the contractions produced   
by the gold tooth pick1 since the       
circumstances both of that case1 and  of
 the experiment related1 were probably  
the same1 two metals in  contact with   
each other4 ,the gold in immediate      

contact with a nerve2  and the silver   
case communicating with it1 and the     
muscles through the  medium of the      
moisture1 with which the whole was      
perhaps surrounded4  ,this led me to    
examine the chain1 and the cannula4 ,i  
found both the  links of the one1 and   
the sides of the other1 soldered with a 
different  metal#c4 ,so that1 in these  
cases1 two metals had at the same time  
been  in contact with a nerve1 with     
moisture1 and with each other4          
,however this may be with respect to the
 necessity of mutual contact1  between  
two different metals in order to excite 
contractions1 ,i have  long ago found1  
that contractions may be excited in an  
animal1 when no  more than one metal is 
in contact with it#d4    ,at the time ,i
 first observed this fact1 ,i was making
 experiments to  ascertain whether it   
was possible to transmit the influence1 
which had  excited contractions in one  
leg1 into another1 removed to some      
distance  from it1 and communicating    

with it1 only by means of a single      
conducting substance1 7such as silver1  
for example74 ,for this purpose1  ,i had
 separated from the trunk1 and from each
 other1 the hind legs of a  frog        
recently killed1 and had detached their 
nerves as far as the knee4  ,i then laid
 them at some distance from each other1 
upon a plate of  glass1 and included the
 nerve of one leg1 and the foot of the  
other1 in  the folded ends of a silver  
chain4 ,with one hand ,i now raised from
 the  muscles1 upon the end of a silver 
probe1 the nerve of the leg1 whose  foot
 was folded in the chain2 and with a    
piece of zinc1 in the other  hand1      
touched1 at the same time1 the nerve and
 the probe4 ,this leg was  thrown into  
strong contractions2 but none were      
excited in the other4 ,i  then touched  
the chain1 and nerve of the other1 and1 
to my surprise1  both legs instantly    
contracted4 ,i had observed1 in the     
beginning of  ,november last1 that it   
was not necessary for the metals to be  

in  contact with any thing but nerve1 in
 order to excite contractions in  the   
muscles1 to which it was distributed2   
and had mentioned this fact  immediately
 afterwards to the ,medical ,society of 
this place1 as a  sufficient refutation 
of the theory1 which ,dr ,valli had     
formed of  ,galvani's discovery4 ,it    
would not1 therefore1 have surpassed my 
expectations1 had the influence1 excited
 by the mutual contact of a  piece of   
zinc1 and probe1 with the nerve1 passed 
through the medium of  the chain1 from  
the leg1 in which it first excited      
contractions1 and  produced contractions
 in the distant leg4 ,but1 ,i now       
thought that ,i had  not only passed the
 influence from one leg to the other1   
but in one of  the legs in a direction  
contrary to the course of its nerves4   
,the  removal of the leg1 whose nerve   
communicated with the chain1 convinced  
me of my error3 but1 at the same time1  
discovered to me a fact of much  greater
 importance1 than any with which ,i had 

hitherto been acquainted4  ,for now1    
upon touching the chain alone with the  
zinc1 ,i found that the  leg1 whose foot
 it still included1 and whose nerve ,i  
held suspended  upon a probe1 contracted
 as strongly as before4 ,the influence  
of the  two metals1 in contact with the 
nerve of the other leg1 had not1        
therefore1 passed into1 and excited     
this4    ,it had from the first been    
known1 that contractions could be       
excited by  placing two different metals
 in contact1 one with the nerve1 the    
other  with the muscles1 and making a   
communication between them3 but1 in this
  experiment1 the only metal in contact1
 either with the nerve1 or  muscle1 was 
silver4 ,neither had the influence      
passed through the chain1  and up the   
leg against the course of the nerve1 in 
consequence of a  communication by means
 of moisture subsisting between the     
zinc1 and the  foot1 as well as between 
the silver chain1 and the foot2 for the 
experiment succeeded equally well when  

the chain was removed1 and the  foot    
laid upon a silver plate made perfectly 
dry4 ,but when either the  zinc1 or     
probe was held by another person not    
communicating with me2 or  when either  
of them was insulated in a stick of     
sealing wax2 no  contraction whatever   
took place4 ,neither1 indeed1 were      
contractions  excited in any part of the
 leg1 except the foot1 when the probe   
was  withdrawn from the nerve2 and the  
foot1 and silver1 were both touched     
with the zinc4 ,it is then clear1 that  
the influence1 which1 in the  former    
case1 excited the whole leg to          
contraction1 must have passed  through  
the medium of my body4 ,it is not       
necessary that the silver  should be    
laid under the foot2 all that is        
required1 is1 that it should            
communicate with it by means of         
moisture2 it may then be laid at almost 
any distance from it#e4    ,the course  
of this influence1 however1 was still   
undetermined3 it might  be from the     

muscles to the nerve3 it might be from  
the nerve to the  muscles4 ,to ascertain
 this1 and to prove that the influence1 
which had  excited one limb to          
contraction1 might pass on1 through a   
foreign  medium1 and excite contractions
 in another1 ,i made the following      
experiment4    ,the leg of a frog was   
disposed as in the former experiment4   
,the probe1  suspending the nerve1 was  
held by myself2 the zinc excitor by     
another  person2 and the leg of another 
frog formed the communication betwixt   
us4 ,so long as ,i had hold of the      
nerve1 and the person assisting me  held
 the foot of this interposed leg1 no    
contractions were excited in  it1 by the
 influence1 which passed through it and 
excited the other  leg4 ,but when the   
person holding the zinc1 held the nerve 
of the  interposed leg2 and ,i held the 
foot1 both legs contracted with equal   
strength4 ,from this experiment it is   
evident1 that ,galvani's influence  had 
passed either from the muscles1 or the  

zinc and silver2 and in the  direct     
course of the nerves of both legs4    ,i
 was now in possession of an easy method
 of ascertaining the different          
substances1 which do1 or which do not1  
afford a passage to this new  influence4
    ,all the metals when pure appear to 
be excellent conductors2 not quite  so  
good when in the ore2 and1 ,i think1    
least so when combined with  acids1     
forming metallic salts4 ,they are       
however1 in this state1 by no  means bad
 conductors1 even when so carefully     
dried1 as to leave no  suspicion of the 
slightest degree of moisture adhering to
 their  surface4 ,but1 when the metals  
are calcined1 their capacity as         
conductors is quite destroyed3 at least 
this was the case with the  calces of   
zinc1 of bismuth1 of iron1 and of       
mercury2 the only ones1  with which ,i  
have had an opportunity of making the   
experiment4 ,i could  not observe that  
any contractions were excited through   
the medium of  stones1 nor ever through 

barytes4    ,the different              
non-conductors of electricity are       
likewise1 ,i find  non-conductors of    
this influence3 even wood1 charcoal1 and
 linen1 do  not conduct except when     
moist4 ,but all the living vegetables ,i
 could  procure afforded it a ready     
passage3 probably from the fluids which 
they contain4 ,while ,i held the probe  
which supported the nerve1 ,i  touched  
the shoe of a gentleman1 who applied the
 zinc to the silver  under the foot of  
the frog4 ,strong contractions were     
excited1 but when  he took off his shoe1
 and we held it between our hands1 no   
contractions  could be excited4 ,in the 
first case1 the influence had to pass   
through  no more than the thickness of  
the shoe3 in the second1 through its    
whole length1 which might not be all    
equally moist4 ,this gentleman had  on  
thread stockings4 ,when ,i touched the  
foot of another1 who had on  cotton     
stockings1 no contractions were excited4
 ,cotton is a  non-conductor of         

electricity4    ,oils of all kinds are  
so far from conducting1 that if the     
fingers of  the person holding either   
the probe1 or the zinc1 have perspired  
much1  even this operates as a complete 
obstruction to the passage of the       
influence3 the instant the perspired    
matter has been wiped away1 and  the    
fingers have been dipped in water1 it   
again passes1 and excites  contractions4
 ,when the intestines of a frog are     
removed1 and its  abdomen is filled with
 oil1 no contraction can be excited by  
placing  one metal upon its sciatic     
nerves1 and bringing another in contact 
with  it1 either above or below the     
surface of the oil4    ,there is        
something singular in this respect1 with
 regard to mercury4 ,if  the abdomen of 
a frog be filled with it1 a piece of    
zinc passed through  it1 so as to touch 
the sciatic nerves1 excites             
contractions4 ,but a  piece of silver1  
passed to them1 excites none4 ,neither  
are any excited  by touching the silver1

 beneath the surface of the mercury1    
with a  piece of zinc4 ,but ,i have     
before shewn1 that1 when water is used  
instead of mercury1 contractions may be 
in this way excited2 yet  mercury is    
reckoned a much better conductor of     
electricity than water4  ,i have        
repeatedly passed this influence through
 a great length of thin  brass wire1 and
 through the bodies of five persons     
communicating with  each other1 by      
dipping their fingers in basins of water
 placed between  them2 yet it did not   
appear to have lost any of its force1 in
 this long  and diffused passage3 for   
the contractions excited in the frog's  
leg  were equally strong1 as when it had
 passed only through one person4        
,vitriolic acid1 and alcohol appear     
still better conductors than water4     
,wishing to ascertain whether it passed 
over the surface1 or through the        
substance of metals1 ,i coated several  
rods of different metals with  sealing  
wax1 leaving nothing but their ends1 by 

which they were held1  uncovered4       
,contractions were excited as readily   
through the media of  these1 as if they 
had not been coated4 ,it seems to meet  
with no  obstruction in passing from    
link to link1 of several chains1 even   
when  no pressure1 except that of their 
own weight1 is used to bring them  into 
contact4 ,i was led from this to hope1  
that ,i should be able to  make it pass 
through a very thin plate of air4 ,i1   
therefore1 coated a  stick of sealing   
wax1 with a plate of tin-foil1 and then 
made an almost  imperceptible division  
a-cross it with a sharp pen-knife4 ,but 
even this  interruption of continuity in
 the conductor was sufficient           
effectually  to bar its passage4    ,the
 chains1 through which it passed most   
readily1 were of gold and  silver4 ,it  
did not pass through a very long and    
fine brass chain1  unless as much force 
as could be used1 without breaking the  
chain1 was  employed to bring its links 
into close contact4    ,i next proceeded

 to examine if the capacity of different
 substances1 as  conductors1 or         
non-conductors1 was at all affected by  
differences of  their temperature4 ,but 
this was not the case with zinc1 iron1  
water1  coal1 or a common crucible1 the 
only substances with which ,i tried the 
experiment4 ,a red hot iron1 and boiling
 water1 conducted equally as  well as   
iron and water that had not been heated3
 and neither the  crucible1 nor the     
coal1 became conductors from any        
addition of heat4    ,i at first thought
 that ice conducted2 but as1 on some    
trials1 no  contractions were excited   
through its medium2 and as it appeared  
uniformly to conduct ill in proportion  
to the dryness of its surface2 ,i       
suspect that1 if perfectly dry1 it would
 not conduct at all4 ,the  instant a    
part of its surface had been dissolved  
by the heat of the  room1 contractions  
were excited with as much ease1 as they 
usually are  through a bason of water4  
,it would appear1 therefore1 that       

neither very  hot1 nor very cold water  
disperse this influence1 as has been    
asserted  by ,dr ,valli1 nor do they    
seem in the least degree to diminish its
 power  of producing contractions#f4    
,it appears upon the whole to be        
necessary1 that this influence should   
pass to a part in a very condensed      
state1 in order to excite  contractions3
 although there are some facts1 which1  
without reflecting1  might lead one to  
suppose1 that1 passing even in a        
diffused state1 it  would excite them4  
,in making that experiment1 in which the
 piece of  zinc under the foot of a frog
 is touched with zinc1 while its crural 
nerve is supported by a silver probe2 no
 contraction takes place1 if  the probe 
be either lowered1 so as to come in     
contact with the muscles  of the thigh1 
or if it be made to touch the silver    
under the foot4    ,if again1 two       
persons1 one of whom holds the probe1   
the other the zinc1  communicate with   
each other by dipping their unemployed  

hands in a  bason of water2 and the     
person using the zinc holds another leg 
of a  frog1 suspended between his       
fingers by its nerve beneath the surface
 of  the water2 no contraction will take
 place in this leg1 when the silver     
under the other is touched with zinc1 at
 the same time that strong ones  are    
excited in that other4 ,but1 if its     
nerve be raised above the  surface of   
the water1 it then contracts as vividly 
as the other4 ,it  appears that in the  
last of these instances1 at least the   
greater part  of the influence had      
diffused itself through the water1      
instead of  passing directly through the
 nerve1 from the fingers of the person  
holding it1 and that in both it had     
passed into the legs1 in too  diffused a
 state to excite them to contraction4   
,i have often likewise observed1 that   
when the nerve of a nearly  exhausted   
leg of a frog had been laid upon a piece
 of zinc1 and both  were touched with   
silver1 the contractions excited were   

very distinct3  but when the zinc was   
placed in contact with the muscle1 as   
well as  with the nerve1 either no      
contractions could be excited1 or such  
feeble  ones that they were scarcely    
perceptible4    ,contractions1 however1 
certainly may be excited in different   
parts of a  frog1 without making any    
division of its skin1 by laying the part
 of  the frog to be excited upon a plate
 of zinc1 or tin-foil1 and passing a    
piece of silver over it1 till all three 
are in contact with each  other#g4 ,yet 
even here the influence does not pass   
into the part in so  diffused a state as
 it may at first appear to do4 ,for the 
skin of these  animals is abundantly    
supplied with nerves1 whose trunks      
communicate1  at different places1 with 
those which supply the muscles4 ,and the
  contractions are always strongest1 and
 most readily excited1 when the  silver 
is passed over the course of any of the 
nerves1 which go to the  muscles4       
,from the fact1 which ,i have before    

mentioned1 that a limb may be made  to  
contract1 when the metals have          
apparently no communication with any    
part of it except its nerve2 it might   
reasonably be doubted1 whether1  in any 
case1 a communication between the       
muscles1 as well as the nerve1  and the 
metals1 were necessary1 in order that   
contractions may be  excited4           
,several considerations1 however1 induce
 me to believe1 that such  communication
 is absolutely requisite4 ,if the       
contact of two different  metals were   
alone sufficient to excite contractions2
 contractions  should always take place1
 whenever a good conductor is interposed
  between the metals1 and the nerve     
alone4 ,but ,i have1 in no instance1    
observed this to be the case4 ,in the   
experiment1 where the crural nerve  must
 be supported upon a silver probe1 it is
 necessary that the piece  of silver1   
with which the zinc is brought in       
contact1 should  communicate either     
immediately1 or through some good       

conducting medium1  with the muscles of 
the foot1 or leg1 before any contraction
 takes  place4 ,and even in the         
experiment1 where water forms the only  
communication between the metals1 and   
the origin of the sciatic nerves1  that 
same water1 it must be observed1 forms  
likewise a communication  between the   
metals and the muscles1 to which these  
nerves are  distributed4 ,but the fact1 
which appears to me most decisive of    
this  question1 is the following3 ,when 
a nerve1 which for some time has been   
detached from surrounding parts1 is     
either carefully wiped quite dry  with a
 piece of fine muslin1 or 7lest this    
should be thought to injure  its        
structure17 suffered to remain suspended
 till its moisture has  evaporated2 no  
contractions can be excited in the      
muscles1 to which it  is distributed1 by
 touching it alone with any two metals  
in contact  with each other4 ,but1 if it
 be again moistened with a few drops of 
water1 contractions instantly take      

place3 and1 in this way1 by  alternately
 drying and moistening the nerve1       
contractions may1 at  pleasure1 be      
alternately suspended and renewed for a 
considerable time4  ,it may1 indeed1 be 
contended1 that the moisture softened1  
and thus  restored electricity and free 
expansion to the dried cellular membrane
  surrounding the fibres1 of which the  
trunk of a nerve is composed2 and  thus1
 by removing constraint1 gave free play 
to their organization#h4    ,but from   
observing1 that1 in every other         
instance1 where contractions  are       
produced by the mutual contact of the   
metals1 a conducting  substance is      
interposed between them and the muscles1
 as well as  between them and the nerve2
 ,i think it would be unphilosophical   
not to  allow1 that1 in the instance in 
question1 the moisture1 adhering to the 
surface of the nerve1 formed that       
requisite communication between the     
metals and the muscles4    ,i relate the
 following fact1 in this place1 because 

at the same time  that it gives further 
confirmation to the above opinion1 it   
affords an  instance in which insulation
 diminished the effect of the metals4 ,i
 had  one day laid the nearly exhausted 
leg of a frog upon my hand1 with a      
piece of zinc in contact with its nerve 
only2 and1 when ,i touched these  with a
 silver probe1 tolerably strong         
contractions were excited1 even  when   
the nerve appeared dry3 but when both   
the leg and the metals1 thus  disposed1 
were insulated by means of glass and    
sealing wax1 the  contractions were     
scarcely perceptible4 ,my hand1 it would
 appear1 had1  in these instances1      
supplied the place of the moisture in   
the other2  and been the conducting     
medium between the muscles and the      
metals4    ,this communication of the   
muscles with the nerve1 through the     
medium of  the metals1 had appeared to  
,dr ,valli a circumstance so essential  
to the  production of ,galvani's        
phenomena1 that 7taking it for granted  

they  were occasioned by the action of  
the electrical fluid71 it seems to  have
 suggested the hypothesis1 which he has 
offered in order to account  for them4  
,aware that no electrical phenomenon can
 possibly have place1 except  between   
the opposite states of positive and     
negative electricity1 or1  in other     
words1 where there is a breach of       
equilibrium in the  distribution of the 
electrical fluid2 he supposes it to be  
one office  of the nerves1 to produce   
this breach of equilibrium1 by          
continually  pumping 7to use his own    
expression7 the electrical fluid from   
the  internal parts of muscles1 and in  
this way rendering them negative1  with 
respect to the external surface4 ,the   
brain1 he makes the common  receptacle  
for this fluid4 ,the metals1 he seems to
 consider in the  light of a conductor1 
interposed between the outside of       
muscles and  their nerves4 ,and the     
rapid transmission of the fluid to      
restore the  equilibrium1 as the cause  

of the contractions4    ,he presumes his
 hypothesis proved from the following   
considerations3    ,i4 ,the interval    
which commonly takes place between the  
contractions2  which interval1 according
 to him1 is necessary for the           
restoration of  the breach of           
equilibrium4    ,,ii4 ,from observing1  
that fishermen1 in order to preserve    
their fish  from putridity1 crush their 
brains2 and thus1 by interrupting the   
medium between the external and internal
 surfaces of muscles1 prevent  these    
repeated discharges of the electrical   
fluid1 which1 according to  ,dr ,valli1 
hastens their putridity4    ,,iii4 ,from
 finding that in general1 when the      
sciatic nerve on one side  of a living  
frog was divided1 the other being left  
entire1  communicating with the brain1  
both armed and equally excited1 the     
limb1  in which the nerve had been      
divided1 preserved its power of         
contracting  longer than the other4     
,from this well devised experiment1 he  

concludes1  likewise1 that animal       
electricity is the principle of life4   
,that1 on  the side where the nerve     
remained entire1 it was withdrawn from  
the  muscles1 and deposited in the      
brain4 ,that1 from the impossibility of 
this taking place on the other side1    
where the nerve was divided1 it  had    
continued in the limb1 and enabled it to
 contract4    ,if it were indisputably  
true1 as ,i once believed1 that         
contractions  could be excited in a limb
 without the metals having any          
communication  with it1 except through  
the medium of a nerve2 this circumstance
 would  alone be a sufficient refutation
 of ,dr ,valli's hypothesis3 but1 as ,i 
have already shewn1 that contractions   
were not in this way produced in  any   
experiment1 which ,i have made1 when no 
moisture1 forming a  communication      
between the metals and the muscles1 had 
been left  adhering to the surface of   
the nerve1 it becomes necessary to have 
recourse to less dubious arguments4     

,the ,dr should have recollected that1  
in cases of a breach of  equilibrium in 
the distribution of the electrical      
fluid1 all that is  required1 in order  
to restore equality of distribution1 is1
 the  interposition of a single         
conducting substance between the place  
in  which it abounds1 and that in which 
there is a deficiency4 ,whereas1 in  the
 phenomena1 which he attempts to        
explain1 two conducting substances  are 
necessary to the effect4    ,when a     
separated limb is placed under water1   
one would naturally  imagine1 that from 
the perfect communication1 which is then
 formed  between the external surfaces  
of muscles and their nerves1 no breach  
of  equilibrium could possibly have     
place3 yet we find ,galvani's phenomena 
even more readily produced in this      
situation1 than when both muscles  and  
nerves are free from surrounding        
moisture4    ,the following experiment  
was made with a view of rendering the   
equilibrium of the electrical fluid1 in 

different parts of frogs1 as  perfect as
 possible4    ,the head of a frog having
 been separated from its body1 the      
latter was  laid upon a plate of zinc1  
held by a person sitting in an insulated
  chair1 which communicated with the    
prime conductor of an electrical        
machine4 ,the machine was put in action1
 and both the person and the  frog were 
electrified positively4 ,in these       
circumstances1 no sparks  could be drawn
 from the frog1 by the person holding   
it3 nor could any  other electrical     
appearance take place between them4     
,but1 when a piece  of silver was passed
 over different parts of the frog1 and1 
at the same  time1 brought into contact 
with the zinc plate1 contractions were  
uniformly excited1 differing not in the 
least1 either in strength or  frequency1
 from those which are excited when no   
artificial electricity  is present4 ,the
 result was precisely the same1 when the
 frog and the  person holding it were   
negatively electrified4 ,this experiment

 was  often repeated4 ,the following    
experiment was made1 in order to see if 
the effect produced upon a frog1 by the 
passage of artificial  electricity from 
any part of its body1 would be increased
 by employing  two different metals as  
conductors4    ,a frog was laid1        
successively1 upon a number of different
 metals1  insulated upon glass1 and     
positively electrified by communicating 
with  the prime conductor of an         
electrical machine4 ,the contractions   
produced  in the frog1 thus disposed1 by
 drawing sparks from it1 with metals    
different from those on which it was    
placed1 were not in the least  stronger1
 than those occasioned by drawing       
similar sparks from it1 with  conductors
 of the same metal4    ,in establishing 
a communication between two opposite    
electricities1 as1  for example1 between
 the two sides of a charged phial1 it is
 matter of  indifference to which the   
conductor is first applied4 ,but it is  
by no  means so1 in the case of muscles 

and armed nerves4 ,for1 if one branch   
of a conductor be applied to the        
tin-foil arming a nerve1 before the     
other branch has been applied to the    
muscles1 it frequently fails to  excite 
contractions4 ,if first applied to the  
muscles1 this is very  seldom the case4 
,as for the intervals of rest which     
alternate with the contractions1 and    
which the ,dr considers as employed by  
the nerves1 in restoring the  breach of 
equilibrium between the internal        
surfaces of muscles1 and  their         
external2 these may possibly admit of a 
different explanation4    ,we find them 
alternating with contractions however   
excited4 ,it is  difficult to conceive1 
that violent contractions should not    
derange in  some degree1 however slight1
 the intimate organization of muscular  
fibres3 and some time must necessarily  
elapse before their elasticity  can have
 restored the organized particles1 of   
which they are composed1  to that       
relative situation with respect to each 

other1 which will fit  them for again   
contracting4    ,this explanation is    
drawn from observing the following      
facts4 ,hearts1  taken from the living  
thorax1 and exposed to the action of a  
strong  stimulus1 contract vividly for a
 time1 and then cease to be effected by 
any further application4 ,if they be    
then removed from the stimulus1 and     
placed for a time either in cold water  
or in open air1 they are  observed to   
regain their susceptibility of the      
action of stimuli1 and  again contract4 
,mr ,coleman1 in his excellent          
dissertation on ,suspended              
,respiration1 makes an observation1     
which ,i have often had opportunity  of 
verifying3 that hearts distended with   
blood1 and in which no  contraction can 
be produced1 by scratching their surface
 with a pointed  instrument1 contract   
spontaneously1 if one of the large      
vessels1 at  some distance from them1 be
 cut so as to evacuate some of the      
blood4    ,the organization1 in this    

case1 is suffered to recover by the     
removal  of the stimulus1 7distention7  
which had deranged it4 ,even1 in the    
living and entire animal1 the heart does
 not renew its contractions1 on  the    
first influx of blood4 ,some time must  
elapse1 while it recovers  from the     
derangement occasioned by the preceding 
contraction4    ,i have repeatedly      
excited1 by means of zinc and silver1   
contractions in  the leg of a frog1     
whose head had been divided from its    
body1 upwards  of three days before4    
,the receptacle1 for the electrical     
fluid1 was in  these cases removed4     
,now1 either the nerves continued       
extracting it  from the internal parts  
of muscles1 or they did not4 ,if they   
did1  having no longer a receptacle1 in 
which they could deposite their         
electricity1 they must have remained    
positively electrified2 and thus1  being
 in the same state with the outer       
surface of the muscles1 no  contraction 
should1 according to the hypothesis1    

have been excited by  the application of
 the metals4 ,but this is contrary to   
the fact4    ,if it be contended1 on the
 other hand1 that their pumping power   
had  ceased2 then the first application 
of the metals1 which produced a         
contraction1 having restored the        
equilibrium1 which could not  afterwards
 be broken1 must have precluded the     
possibility of further  contractions4   
,but this too is contrary to fact4      
,this argument appears1 to me1 to do    
away all support1 which the  hypothesis 
may seem to derive from the experiment1 
before quoted1 of  applying the metals  
equally to both sciatic nerves1 after   
one of them  had been divided2 ,i may   
however remark1 that the pain           
necessarily  excited by arming a nerve1 
whose communication with the brain was  
not  interrupted1 would fully account   
for the more rapid exhaustion of the    
muscles1 to which it belonged1 compared 
with such as had not been acted  upon by
 so strong an additional stimulus4 ,as  

fact1 however1 is always  more          
satisfactory than argument1 ,i shall    
relate the following  accidental        
experiment1 in proof of the relevancy of
 the foregoing  observation4    ,four   
days after ,i had divided the crural    
nerve of a female frog1 full  of spawn1 
,i found her dead2 she had been observed
 alive the night  before4 ,the          
application of the metals to the leg1   
whose nerve had not  been divided1 did  
not excite the slightest contractions1  
but on  applying them to the leg1 in    
which the nerve had been divided1       
tolerably strong contractions were      
excitable1 for more than twelve  hours  
after she was found4 ,the spawning      
season had closed1 upwards of a  week   
before this happened1 and1 as this frog 
had long been without a  male to assist 
her1 it is probable1 that her death had 
been occasioned  by the retention of her
 spawn1 as it was found in a very       
dissolved  state4 ,the pain1 necessarily
 preceding such a death1 could affect   

the  different parts of the animal1 only
 through the medium of its nerves2  and 
hence the exemption of that part from   
its effects1 to which the               
communication1 by nerve1 had been       
interrupted4    ,the same observation   
will apply to that argument1 which ,dr  
,valli has  drawn1 in support of his    
hypothesis1 from the practice of        
fishermen4 ,by  destroying the brain1   
they take away all sense of pain1 and1  
consequently1 preclude that exhaustion  
which is so notorious for  disposing to 
putridity4    ,should it1 therefore1 be 
ever proved1 that the phenomena         
discovered by  ,galvani are effects of  
the action of electricity1 ,i cannot    
think ,dr  ,valli's hypothesis will be  
deemed a satisfactory account of the    
manner  in which it produces them4      
,strong1 however1 as is the analogy1    
which1 in many particulars this         
influence bears to electricity1         
considerable doubts must1 ,i think1     
still remain as to their identity4      

,the grounds of these doubts would best 
appear in an accurate and full          
statement of the several points1 both of
 resemblance and of difference  between 
this influence1 electricity1 and that   
power which distinguishes  the torpedo1 
the gymnotus1 and the silurus2 but1 ,i  
can here promise no  more than a very   
imperfect and desultory sketch of these4
    ,in order to accumulate artificial  
electricity1 if ,i may be allowed the   
use of such an expression1 it seems     
necessary1 that there should be  motion 
between two substances1 an electric and 
a conductor4 ,but1  neither motion nor  
electrics have any share in the         
production of that  influence which     
occasions the phenomena in question4    
,the motion1 here1  is the effect1 and  
not the cause of the accumulation3 and  
instead of  one conducting substance of 
any kind whatever1 two metallic         
substances  seem indispensably          
requisite#i4    ,that influence1        
whatever it be1 which is possessed by   

the torpedo1 c4  seems to depend        
entirely upon the will of these animals1
 both for its  production1 and          
management1 as appears not only from the
 retraction of  their eyes within their 
sockets1 whenever they mean to give a   
shock1  but1 likewise1 from each shock  
being increased1 diminished1 or         
withheld1 as they are irritated or aware
 of some obstacle to its  transmission4 
,but the will of an animal has no share 
in the production  of the phenomena     
discovered by ,galvani4    ,in the scale
 of conductors of electricity1 charcoal 
holds a higher  place than the fluids of
 animal bodies1 and ice than the        
metallic  salts4 ,but of the influence  
in question1 ,i have found animal       
fluids1  and metallic salts1 excellent  
conductors1 at the same time that ,i    
have  never observed it pass through    
charcoal1 or even dried wood4 ,i have1  
likewise1 reason to believe that it does
 not pass through ice4 ,ice1  indeed1 is
 but a very imperfect conductor of      

electricity1 when free  from air        
bubbles1 and when the experiments with  
it are made in a very  low degree of    
temperature4 ,yet we are told by ,mr    
,achard1 that it will  conduct          
electricity1 even when ,reaumur's       
,thermometer stands at #f  degrees below
 #j4    ,but the temperature of the     
room1 in which ,i made my experiments1  
was at  least #ee degrees above #j1 by  
,fahrenheit's scale4 ,i may likewise    
remind  the reader of the experiment1 in
 which the abdomen of a frog was filled 
with mercury1 and a rod of silver passed
 through it to the sciatic  nerves4 ,a  
piece of zinc1 touching both mercury and
 silver1 excited no  contractions2      
whereas most vigorous ones were excited 
when water was  substituted for the     
mercury4 ,a proof1 as ,i take it1 that  
water is a  much better conductor of    
this influence than mercury3 but of     
electricity1 mercury is deemed a better 
conductor than water4    ,we are told by
 ,mr ,cavendish1 that ,mr ,walsh found  

the shock of the  torpedo would not pass
 through a small brass chain3 but the   
influence  discovered by ,galvani1      
passes1 without sensible diminution of  
its  effects1 through a small brass     
chain of several inches in length1 when 
it is drawn so tight as to bring its    
links into close contact with each      
other3 and it passes through a gold     
chain when held between two  persons1   
and suffered to hang with a considerable
 bend4 ,yet1 if we may  be allowed to   
judge of the comparative strength of the
 two influences1  by the effects which  
they produce upon animals1 that of the  
torpedo  must certainly be allowed to be
 the strongest2 and ,i see no other way 
of accounting for its finding an        
insuperable obstacle to its             
transmission1 where the other finds     
scarcely any1 except by supposing  that 
they are in reality different in their  
nature4    ,dr ,valli tells us1 that he 
observed the hairs of a mouse1 attached 
to  the nerves of frogs by the tin-foil1

 with which he surrounded them1         
alternately attracted1 and repelled by  
each other1 whenever another  metal was 
so applied as to excite contractions in 
the frogs4    ,this experiment ,i have  
many times repeated1 both in the manner 
described by the ,dr1 and with every    
variation in the disposition of the     
hairs which ,i could devise3 but whether
 they were placed upon the  metals1 the 
nerves1 or the muscles1 or upon all at  
the same time1  neither ,i1 nor my      
friends who assisted me1 have in any    
instance been  able to observe them     
agitated in the slightest degree4    ,i 
have made similar experiments upon a    
dog1 and upon a large and lively  skate1
 by disposing1 in the same way that ,i  
did the hairs of a mouse1  flakes of the
 finest flax1 swansdown1 and gold leaf2 
but although the  contractions produced 
in the skate1 by the contact of the     
metals1 were  so strong as to make the  
animal bound from the table1 not the    
least  appearance of electricity was    

indicated4    ,i next suspended1 from a 
stick of glass fixed in the ceiling of a
 close  room1 some threads1 five feet in
 length1 of the flax which ,i used in   
the former experiment2 and approached   
some frogs1 recently killed1 and        
insulated upon glass as near to them as 
was possible1 without touching3  but the
 threads were in nowise affected by the 
contractions produced in  the frogs4    
,in this respect1 therefore1 this       
influence agrees with that of the       
torpedo1 c4 ,so far as ,i know1 ,m4     
,volta's instrument for collecting1     
condensing1 and rendering sensible1 very
 small degree of electricity  has not   
been employed in the examination of     
either4    ,and indeed ,i am not sure1  
if1 in examining the newly discovered   
influence1 by such a test1 a sufficient 
quantity of electricity might  not be   
produced merely by the motion of the    
animals1 subjected to the  experiment1  
to occasion some fallacy in the result4 
,certain1 however1  it is1 that although

 this influence did not affect the      
electrometer in  these experiments1 it  
produces infinitely stronger effects    
upon an  animal1 than any which can be  
produced by a quantity of electricity   
sufficient to affect an electrometer to 
a very high degree4 ,i have  frequently 
detached the crural nerves of frogs for 
some length2 and  having supported them 
upon a rod of silver1 have applied an   
excited  piece of glass1 or sealing wax1
 to the whole length of this rod4 ,the  
coarsest electrometers have been        
effected by it1 at considerable         
distances3 but ,i have never1 in this   
way1 been able to excite  contractions1 
unless by laying the rod upon the       
excited cylender of a  powerful         
electrical machine4    ,this new        
influence likewise resembles that of the
 torpedo1 in producing  its effects     
almost equally well1 when both it and   
the subject upon  which it acts are     
insulated from surrounding conductors4  
,but an  experiment similar to that1    

which ,i have related1 of insulating1   
and  positively electrifying1 both the  
frog and the metals applied to it1  has 
never 7so far as ,i am acquainted17 been
 tried with the torpedo4    ,both these 
influences agree too1 in not producing  
so strong an effect1  when the subject1 
upon which they act1 is immersed in     
water1 as when it  is in the open air4  
,when the separated leg of a frog was   
held under  water1 and formed part of   
the circuit through which this1 to      
influence1  had to pass1 in order to    
excite another leg2 it never contracted1
  although it did1 and strongly1 when   
held above the surface1 as ,i have      
already had occasion to notice4 ,and we 
are told by ,mr ,walsh1 that the  shock 
of the torpedo was four times stronger  
in air1 than when given  under water4   
,this influence differs1 both from that 
of the torpedo1 c4 and from             
electricity1 in producing no sensation  
7in man at least17 at all  similar to   
that from an electrical shock4    ,with 

respect to the single instance related  
by ,m4 ,cotugno1 it is  probable that   
both he himself1 and all who have       
repeated experiments of  this nature1   
must have been long ago convinced1 that 
he was deceived  into the belief of a   
shock1 from the sensation produced by   
the  struggles of the animal he         
dissected4    ,that some kind of        
disagreeable sensation is occasioned by 
it1 even in  frogs1 independent of that 
which must necessarily arise from       
irritation1 and the contractions of     
their muscles1 is evident from  their   
restlessness1 and expressions of        
uneasiness4 ,in other animals1 as  ,i   
shall afterwards have occasion to shew1 
these expressions are still  less       
equivocal3 and1 in man1 we can ascertain
 both their degree and  their kind4     
,that they differ considerably from such
 as are produced by  electricity1 will  
be proved when ,i come to speak of the  
effects of this  influence upon our     
senses4    ,but the most important1 and 

characteristic difference1 which ,i have
 yet  been able to discover1 between    
this new influence and electricity1     
consists in their effects upon the      
contractile power of animals and of     
plants4 ,the contractions of animals    
excited by electricity have a  tendency 
to destroy that power upon which        
contractions depend4 ,but the           
contractions excited1 by the application
 of the metals1 have1 in all my         
experiments1 had the directly opposite  
effect4 ,the more frequently            
contractions have been1 in this way1    
excited1 the longer do they  continue   
excitable3 and the longer are the parts1
 upon which such  experiments are made1 
preserved from putridity4 ,an influence1
 capable  of exciting contractions1     
without occasioning exhaustion1 was a   
thing ,i  so little expected to find1   
and so contrary to the character which  
had  been given of this1 both by        
,galvani and by ,dr ,valli1 that ,i1 at 
first1  distrusted my own observation of

 the fact3 but the number of            
comparative experiments1 which ,i had   
afterwards occasion to make1  though    
with views different from that of       
ascertaining the point in  question1    
convinced me that this influence1 so far
 from destroying the  contractility of  
muscles1 has a tendency to preserve it4 
,oxygene is1 so  far as ,i know1 the    
only stimulus in nature1 whose effects  
are at all  analogous4    ,when a frog  
has been long dead1 ,i have been        
sometimes more than a  quarter of an    
hour without being able to excite a     
single contraction by  the application  
of the metals3 but after this1 without  
at all varying  the means employed1     
contractions have appeared1 and have    
become  gradually more and more         
vigorous4    ,it is said1 7for ,i have  
never had an opportunity of making the  
experiment17 that a stream of           
electricity passed through a sensitive  
plant produces an almost immediate      
collapse of its leaves4 ,but the        

influence1 discovered by ,galvani1      
produced no such effect in the          
following experiment4 ,having separated 
the leg of a frog from its body1  ,i    
freed its crural nerve from surrounding 
parts1 and with one hand held  it       
supported upon the end of a probe4 ,an  
assistant placed a piece of  silver     
under its foot1 and held the zinc with  
which it was to be  touched4 ,a         
sensitive plant formed the medium of    
communication between  us4 ,he held the 
bottom of its stem between his fingers1 
while ,i held  the top3 so that when the
 silver was touched by the zinc1 the    
influence  passed up the plant1 and     
through the whole of its stem4 ,the     
frog's leg  instantly contracted1 and   
repeated its contractions every time the
  silver and zinc were in contact3 but  
the leaves of the plant did not         
collapse2 neither did they when any of  
its branches formed part of the         
circuit4    ,i must1 however1 confess   
that the plant1 upon which this         

experiment was  made1 had been kept     
through the winter4 ,with a young one   
the result  might possibly be different2
 but such an one ,i have not yet had it 
in  my power to procure4    ,the torpedo
 does not appear at all affected by the 
influence which  itself produces4       
,animals1 in which ,galvani's phenomena 
are produced1  are strongly affected4   
,from this circumstance1 and still more 
from the  presence of metals being      
absolutely requisite to their           
production1 some  may be induced to     
believe1 that the influence1 which      
causes them1 is  something external to  
animals2 and that it arises from the    
mutual  contact of the metals only4 ,i  
must confess ,i was1 for some time1     
inclined to entertain this opinion2 and 
its probability appeared to be  not a   
little increased by observing that its  
effects differed with the  metals       
employed1 and were strongest when their 
surfaces were extended1  and applied    
horizontally to each other4 ,i began1   

therefore1 to suspect  that it might be 
some hitherto undiscovered property of  
metals2 for  that it was not an         
electrical phenomenon1 seemed still     
further proved  by the circumstance     
above related4 ,it has been             
demonstrated1 by the  very interesting  
discoveries of ,m4 ,volta1 that1        
#8wherever the capacity  of holding     
electricity is greater1 there the       
intensity of electricity  is            
less'3--#8and that the capacity of a    
conductor is increased1 when1  instead  
of remaining quite insulated1 the       
conductor is presented to  another      
conductor not insulated2 and this       
increase is more conspicuous1  according
 as the surfaces of those conductors are
 larger1 and come  nearer to each       
other#aj4'    ,when1 therefore1 a plate 
of silver1 communicating with the leg of
 a  frog1 was laid upon glass1 and a    
plate of zinc was lowered horizontally  
upon it1 the capacities of both1 for any
 electricity which they might  have     

contained1 must have been so much       
increased1 that no one will  suspect the
 contractions of the frog's leg1 to have
 been occasioned by  any discharge of   
the electrical fluid from them4    ,as  
little are we authorised to suppose1    
that the contractions were  produced in 
consequence of the metals attracting the
 electrical fluid  from the leg3 for1   
since the leg was insulated1 it is      
impossible that  it should have received
 a new supply of electricity1 after     
having been  deprived by the metals of  
what it naturally possessed2 and        
consequently1 after once or twice       
contracting1 no further contractions    
should have taken place3 but this is    
contrary to the fact4    ,i have before 
shewn1 that flakes of gold leaf1 placed 
between the  metals1 were not affected  
by their approach to each other2 and    
that1  besides1 a quantity of           
electricity1 sufficient strongly to     
affect an  electrometer1 was far too    
weak to excite contractions in the      

muscles of  a frog4    ,that this       
influence1 however1 whatever it be1 is  
not derived from the  metals alone1 but 
that animals at least contribute to its 
production1  as well as indicate its    
presence1 is1 ,i think1 rendered highly 
probable1 by what ,i have already urged1
 relative to the necessity of a         
communication between the metals1 and   
the muscles1 as well as between  the    
metals and the nerves4    ,i may        
likewise observe1 that animals appear to
 have a much more  complete controul    
over its effects1 than one would expect 
them to have  over an influence wholely 
external to them4    ,when living and   
entire frogs are placed upon a plate of 
zinc1 or  tin-foil1 and a piece of      
silver1 or of gold1 is passed over      
different  parts of their legs1 and     
thighs1 till it come into contact with  
the  plate2 contractions are very seldom
 produced1 and scarcely ever1 if the    
frogs be healthy and upon their guard4  
,but the instant their sciatic  nerves  

are divided1 the contractions produced  
are as free and vigorous1  as if the    
legs had been completely separated from 
the body4 ,this  difference is not owing
 to the silver coming in contact with   
the wound1  necessarily made in order to
 divide the nerve2 for ,i have always   
taken  care that it should not1 and     
indeed when it did1 no contractions were
  produced1 unless the nerve had been   
divided4    ,taking off the head of an  
animal1 or intercepting1 in any way1 the
  influence of its will upon the muscles
 of the part excited1 has  precisely the
 same effect4 ,but the will is not able 
to controul the  effects of electricity1
 when the electricity is otherwise      
sufficiently  strong to excite muscles  
to contraction4 ,i have repeatedly found
 that  even by the strongest voluntary  
contractions of the muscles of my arm1  
,i have not been able altogether to     
counteract the involuntary ones1        
produced by electrical sparks1 nor have 
,i found that frogs could ever          

counteract them4    ,on attending       
carefully to the state of the muscles of
 the legs of  living frogs1 at the      
instant the metals were applied1 ,i     
could perceive  by the touch1 that1 in  
many frogs1 though by no means in all1  
their  muscles were perfectly soft and  
relaxed3 a proof that they have other   
means of counteracting the involuntary  
contractions1 which the metals  have a  
tendency to produce1 besides keeping    
their muscles in a state of  permanent  
and voluntary contraction4    -----     
,footnote #a3      ,cavallo4            
,footnote #b3      ,on this metal       
,cronstedt has the following very       
curious remark3 8,it    seems to become 
electrical by friction1 and then its    
smaller    particles are attracted by   
the loadstone2 which effects are not yet
    properly investigated40 ,zinc is an 
ingredient of the best amalgam for      
smearing the rubbers of electrical      
machines3 ,but ,i have not been able    
to render a bar of zinc electrical by   

friction1 nor to find that its          
smaller particles were in any state     
attracted by the loadstone1    unless   
they had been scraped off by means of an
 instrument of iron4    ,but1 in this   
way1 the dust of any metal is rendered  
susceptible of    the influence of the  
loadstone4    ,footnote #c3      ,if    
further experiments should establish    
decidedly1 that the mutual    contact of
 two different metals is absolutely     
necessary for the    productions of     
,galvani's phenomena1 may not this      
circumstance afford    an useful test of
 the purity of the precious metals8 ,for
 instance1    contractions in an animal 
produced by the contact of a piece of   
gold    or silver1 whose purity we wish 
to ascertain1 with a piece of the       
same metal known to be pure1 would then 
prove incontestably the    presence of  
alloy4    ,footnote #d3      ,in an able
 lecture1 which ,dr ,monro lately       
delivered1 chiefly upon    this subject1
 he demonstrated the possibility of     

exciting    contractions in the limb of 
a frog1 without either of the metals he 
employed being in contact with it2 or   
having any other communication    with  
it than through the medium of some moist
 substance4 ,in varying    this         
experiment1 ,i find1 that if a frog be  
divided in two parts1 just    above the 
origin of the sciatic nerves1 and put   
into a bason of    water1 the hind legs 
may be thrown into strong contractions1 
by    bringing zinc1 or tin-foil1 and   
silver1 in contact with each other1     
at the distance of at least an inch from
 the divided spine1 so long    as they  
are kept nearly in a right line with it4
 ,water1 in this case1    is the only   
communication between the metals and the
 origin of the    nerves4    ,footnote  
#e3      ,the contractions produced     
seemed to be strong in proportion to the
    extent of the surfaces of the metals
 in contact1 strongest when a    large  
plate of zinc is laid horizontally upon 
a large plate of silver    or gold4 ,if 

the zinc be suffered to remain in       
contact with the    silver1 for a little
 time1 the contractions of the leg      
cease4 ,the    zinc may then be slid    
over the silver1 till it even touch the 
leg    without renewing the             
contractions3 but1 in withdrawing the   
silver1    the leg contracts at the     
instant the silver parts from it6       
,footnote #f3      #8,l'eau trop        
chauffe1 ou qui est en boullition1      
disperse    l'lectricit1 de manire  en  
dtruire les phenomnes4'      #8,l'excs  
du froid prive l'eau mme de la proprit  
de conduire le    fluide en             
question4'--,dr ,valli1 ,lettre #ime4   
,footnote #g3      ,it was in this way1 
indeed1 that ,i have always excited     
contractions1    when ,i have employed  
this new mode of influencing animals1 as
 a test    of remaining life in any part
 of them4      ,they were constantly    
kept in fresh water1 as the situation   
most    natural to them1 during the     
whole of the time they were under       

experiment2 and their skins were        
suffered to remain as entire as         
possible1 since ,i found their muscles  
lost their contractile power1    in a   
few hours1 and became rigid when        
exposed1 deprived of their    skins1 to 
the action of the water4    ,footnote   
#h3      ,m4 ,fontana1 in the first     
volume of his work on ,poisons1 mentions
 some    facts1 which may1 to some1     
appear to give considerable countenance 
to    this explanation4 ,the            
microscopical eels found in dry and     
smutty    wheat2 the seta equina or     
gordius of ,linnaeus2 and the wheal     
polypus1    all1 when dry1 become       
apparently dead3 but again recover      
motion and    life when moistened with  
water4 ,one of the latter was put1 by   
,m4    ,fontana1 upon a bit of glass1   
and exposed1 during a whole summer1 to  
the noon-day sun4 ,it became so dry that
 it was like a piece of    hardened     
glue4 ,a few drops of water1 however1   
did not fail to restore    it to life4  

,another was1 in this way1 recovered    
after a similar    exposure of a year   
and a half4 ,father ,gumillo1 a ,jesuit1
 and the    ,indians of ,peru1 are      
quoted by the same author1 on the       
authority of    ,bonguer1 as speaking of
 #8a large and venemous snake1 which    
being dead    and dried in the open air1
 or in the smoke of a chimney1 has the  
property of coming again to life1 on its
 being exposed1 for some    days1 to the
 sun1 in a stagnant and corrupted       
water4'      ,but it would almost       
require the credulity of an ,indian to  
credit the    testimony of the ,jesuit4 
,footnote #i3      ,since what ,i had   
before written upon this subject went to
 the press1    ,i have been informed by 
a friend1 that ,dr ,lind of ,windsor has
 found1    that contractions may be     
excited in a frog by touching it with   
iron    alone4 ,in a frog very recently 
killed1 ,i have myself1 sometimes1      
excited contractions1 by touching its   
nerves with iron and steel in           

conjunction4 ,but ,i can by no means    
consider this as a satisfactory         
proof1 that contractions may be excited 
by the contact of one metal    alone2   
since ,i have never been able to excite 
contractions with a    piece of iron1 of
 the same quality throughout1 applied to
 a frog    which had been so long dead  
as to leave no suspicion that the       
contractions were occasioned by         
mechanical irritation4 ,in ,dr ,valli's 
experiment1 with scissars of bad steel1 
upon a frog recently killed1    these   
circumstances do not appear to have been
 sufficiently attended    to4           
,footnote #aj3      ,phil4 ,trans4 vol4 
#gb4 part i4 ,appen4                    
----------------------------------------
--------------------------------        
,,section ,,ii4      ,has ,magnetism any
 concern in the ,phenomena discovered by
 ,galvani8      ,in answer to this      
question ,i have little to say1 as the  
experiments  which it suggested1 and    
which ,i had an opportunity of making1  

have been  but few4    ,i have          
repeatedly excited contractions1 both   
with the natural and the  artificial    
loadstone1 but ,i could never observe   
any difference between  them1 and such  
as were excited by unmagnetised iron1 or
 an ore  containing an equal quantity of
 iron with the natural loadstone4       
,when the separated leg of a frog was   
laid upon a plate of iron1 and a        
loadstone was brought in contact both   
with its nerve and the plate1 no        
contraction was excited4 ,i have often  
brought frogs1 in every state of        
preparation1 as nearly as possible to a 
very sensible magnetic needle1  but no  
variation in its direction was in any   
case produced by the  contractions of   
the frogs excited by the metals4        
----------------------------------------
--------------------------------        
,,section ,,iii4                        
,what are the relations which subsist   
between the influence discovered by     
,galvani1    and the muscles1 the       

nervous1 and the vascular systems1 of   
animals8      ,in proposing to myself a 
question of this very extensive nature1 
it  will hardly be imputed to me1 that  
,i ever entertained1 for a moment1  the 
idle expectation of being able          
completely to solve it4 ,it is  prefixed
 to the following experiments as the    
most commodious general  head under     
which ,i could arrange1 not only what ,i
 had further to say1  upon the influence
 discovered by ,galvani1 but likewise   
upon the several  physiological         
subjects1 in the examination of which   
this influence was  employed merely as a
 test4                                  
,,of ,,the ,,muscles4    ,as ,i am      
acquainted with no criterion by which we
 can assure ourselves  of the complete  
separation of muscular fibres from      
nerves1 without  rendering them objects 
too minute for accurate experiment2 it  
can never  be in our power1 so far as ,i
 am able to judge1 to satisfy ourselves1
 if  this new influence can act         

immediately upon the muscular fibre4 ,a 
doubt  must always remain1 whether nerve
 has not been present2 and from this    
doubt will arise another still more     
difficult to solve1 whether the         
influence produced or excited by the    
metals have passed through the  nerve to
 the muscles8 or if it have merely acted
 as a stimulus to the  nerve1 serving to
 rouse that unknown energy1 by which    
nerves are known  in certain            
circumstances to excite muscles to      
contraction4    ,the following          
experiments1 made upon animals          
considered by anatomists1  in general1  
as destitute of nerves1 may to some     
appear decisive of this  question1 but  
to myself1 ,i confess1 they are by no   
means so4 ,in by far  the greater number
 of animals1 we are precluded from the  
possibility of  discovering nerves by   
their minuteness2 yet the actions of    
these  animals1 not merely excited by   
mechanical irritation1 but so obviously 
directed to the attainment of an end1   

oblige us to infer their  existence even
 where our senses1 aided by the best    
glasses1 do not  enable us to detect    
them4    ,having laid some earth worms  
upon a plate of zinc1 ,i tried to excite
  contractions in them1 by passing a rod
 of silver over different parts  of     
their length1 till it came in contact   
with the plate2 but for a long  time    
without producing any effect4           
,application of the metals to a part    
recently divided seemed to produce as   
little effect4 ,at length1 ,i  perceived
 one of them dart itself forwards1      
whenever the silver was  passed under   
its belly near to a part which had been 
divided and  rejoined4 ,on repeating the
 experiment again1 and with more care1  
,i  found1 7as in the frog17 that when  
the animal was perfectly lively1 and    
upon its guard1 no contraction could in 
this way be excited2 but that  when a   
part had been rendered more sensible by 
previous disease1 recent  irritation1 c4
 or when the worm was taken unawares by 

hanging it over  a probe1 and lowering  
both upon the plate at the same instant2
 a sudden  and involuntary motion seemed
 to dart through a great part of the    
worm's length from the part touched     
towards the head2 a direction  contrary 
to that in which it takes place in other
 animals4 ,i never  could produce the   
same effect upon leeches4 ,on varying   
the experiment1  a most whimsical1 but  
satisfactory phenomenon presented       
itself4 ,i had  laid a leech upon a     
crown piece of silver1 placed in the    
middle of a  large plate of zinc4 ,the  
animal moved its mouth over the surface 
of the  silver without expressing the   
least uneasiness2 but having stretched  
beyond it and touched the zinc plate    
with its mouth1 it instantly  recoiled1 
as if in the most acute pain1 and       
continued thus alternately  touching and
 recoiling from the zinc1 till it had   
the appearance of  being quite fatigued4
 ,when placed wholly upon the zinc1 it  
seemed  perfectly at its ease2 but1 when

 at any time its mouth came in contact  
with the silver lying upon the zinc1 the
 same expression of pain was  exhibited 
as before4    ,with the earth worm1 this
 experiment succeeded still more        
decisively4  ,the animal sprang from the
 zinc in writhing convulsions2 if1 when 
the  worm stretched itself forwards1 one
 of its folds lit upon the zinc1 it     
expressed little uneasiness in          
comparison of what it shewed when the   
point of its head touched the zinc4     
,these extraordinary effects were1      
however1 considerably different from    
those produced by the metals upon the   
limbs of frogs1 and other  animals4     
,they had not so much the appearance of 
involuntary1  instantaneous convulsions1
 as long continued expressions of pain  
and  disgust2 such as are produced by   
applying zinc and silver to the tongue  
of a child4    ,a strong presumptive    
proof1 in my humble opinion1 that these 
animals  are endowed with a most        
exquisite organ of sense1 and1          

consequently1  that they are not1 as has
 been supposed1 destitute of a nervous  
system4    ,doubtful1 therefore1 if this
 influence can ever act upon the        
muscular  fibre1 except through the     
medium of nerves1 ,i shall reserve what 
,i have  to say upon particular muscles1
 till ,i have related some facts        
relative  to the nerves4                
,,of ,,the ,,nerves4    ,it appears from
 every experiment1 which has been made  
in prosecution of  ,galvani's discovery1
 that the nerves are very essentially   
concerned1 in  all the phenomena which  
it exhibits4 ,it becomes1 therefore1 an 
object  of inquiry1 highly interesting1 
to ascertain if all the nerves of the   
body are equally subjects of this new   
influence1 or if its effects are        
confined to those appropriated to       
muscles of voluntary motion4 ,with  this
 view1 ,i surrounded with tin-foil the  
parvagum and intercostal  nerves of     
several cows and sheep1 while the       
auricles of their hearts  were still    

contracting1 and placed one end of a    
bent silver rod1 at one  time upon the  
heart itself1 at another upon adjacent  
muscles1 and  sometimes upon the nerves2
 but all without producing the slightest
  perceptible variations1 in the        
contractions of the heart1 or a renewal 
of them when they had ceased4    ,i     
likewise included the caroted artery in 
the tin-foil2 and1 at another  time1    
inserted the foil in longitudinal       
incisions made in the nerves1  that it  
might be more immediately in contact    
with their substance2 but  still no     
contractions followed4 ,i had as little 
success when ,i made  similar           
experiments upon a dog1 cats1 rabbits1  
fowls1 and frogs2 yet1  in all these    
animals1 ,i could in general excite     
vigorous contractions1  by arming the   
nerves of parts obedient to the will3 ,i
 say in general1  for in rabbits ,i have
 sometimes failed altogether2 especially
 when they  have been drowned in very   
cold water4 ,soon after making these    

experiments1 ,i perceived from one of   
,dr ,valli's letters1 published in  the 
,journal de ,physique1 that he had made 
a similar one upon the heart  of a dog1 
and with the same result4 ,the heart1   
through the medium of  its nerves1 is   
not excitable1 therefore1 by the same   
means which are  found efficacious in   
exciting other muscles to contraction4  
,i confess ,i  had not expected this    
result4 ,it has been asserted indeed1 by
 many  physiologists of the first       
name#aa1 that the heart can in nowise be
  affected by the application of a      
stimulus to its nerves1 or to the       
brain2 but many considerations excited  
my doubts upon this subject1 and  some  
experiments which ,i made at this place1
 more than a year ago1  tended to       
confirm me in an opposite opinion4 ,that
 both the frequency1  and the strength  
of the heart's contractions are affected
 by passions  of the mind1 is a fact    
known to every one2 but what is much    
more to the  purpose1 since we know so  

little either of mind or of its mode of 
influencing the body1 we know that many 
derangements of the brain1 such  as     
apoplexy1 hydrocephalus1 phrenitis1 c4  
together with all kinds of  mechanical  
injuries1 7and what are these1 but so   
many stimuli  irritating the brain1 and 
consequently the nerves sent to the     
heart87  affect the motions of the heart
 most materially and obviously4 ,the    
contractions of the heart1 so long as   
the brain remains entire1 may be        
affected by a thousand different        
substances thrown into the stomach2  but
 it appears from the experiment of ,mr  
,kite1 that this is by no means  the    
case1 when the functions of the brain   
are suspended by hanging1 or            
drowning#ab4 ,dr ,whytt's experiment on 
this subject is one of the most         
decisive with which ,i am acquainted4   
,he found1 that opium operates much     
more slowly in destroying the heart's   
motion in frogs1 deprived of  their     
brain and spinal marrow1 than it does   

when these animals ate  entire4 ,several
 of my own experiments1 though not made 
expressly with  this view1 gave the same
 result with those of ,dr ,whytt4 ,m4   
,fontana  tells us1 he has discovered   
the heart of the wheel polypus to be a  
voluntary muscle4 ,it was probably this 
discovery which led him to try  the     
effects of his will upon his own heart4 
,for the success of his  experiment1 we 
have the testimony of his friend ,dr    
,gerardi1 ,professor  of ,anatomy in the
 ,university of ,parma1 who1 in a very  
learned little  ,dissertation on the    
,origin of the ,intercostal ,nerve1     
published in the  ,journal de ,physique 
for ,september last1 makes the following
 short  mention of it2 #8,je ne dois    
point oublier de vous dire que ,m4      
,fontana a  la facult d'acclrer1 ou de  
retarder  volont son pouls1 sans aucune 
contraction sensible des muscles4'      
,the direct experiments1 by which ,i was
 first led to adopt the opinion  that   
the heart might be affected by the      

mechanical irritation of its  nerves1   
were made upon very young cats and      
rabbits2 some with the  assistance of my
 friend ,dr ,physick1 now settled in    
,philadelphia2 others  in presence of   
several other gentlemen studying at this
 university4 ,it  appeared very         
decidedly from two or three of these    
experiments1 that  the contractions of  
the heart were quickened by irritating  
the brain at  the origin of the spinal  
marrow4 ,in others again1 the result was
 by no  means so clear4 ,but it should  
be recollected that the evidence of one 
accurate1 and positive experiment1 is   
not in the least invalidated by  twenty 
unsuccessful ones1 especially upon      
animals of warm blood2 where  the       
irritability of their muscles is so very
 fleeting1 and the result  liable to    
variation from so many1 as yet1 unknown 
causes4 ,the  irritability of the       
arteries1 for example1 is now completely
  established1 yet ,haller's experiments
 led him to deny it4 ,and even  those of

 the accurate ,verschnir1 to whom we are
 indebted for  unquestionably the best  
series of experiments upon this subject1
 failed  of success 7as we are told by  
,dr ,dennison1 in an excellent ,thesis  
confirming their truth17 when repeated  
before some of the ,faculty here4       
,immediately1 therefore1 on discovering 
the superior powers of zinc1 and        
molybdena1 in exciting contractions1 ,i 
began again to repeat with these  metals
 the experiments on the nerves passing  
to the hearts of frogs2  but for a long 
time without satisfying either myself1  
or others1  whether any effect was      
really produced4 ,at length1 however1 ,i
 was so  happy as to succeed completely4
 ,on the #ahth of ,march last1 in       
presence  of my friends1 ,mr ,hunter and
 ,mr ,thomson1 having dissected away the
  pericardium from a frog's heart1 which
 had an hour before ceased              
spontaneously to contract1 ,i removed   
the muscles1 and cellular membrane      
covering its nerves1 and large blood    

vessels4 ,i then placed one end of  a   
rod of pure silver in contact with one  
side of these nerves1 and  blood        
vessels1 and one end of a rod of zinc on
 the other1 both of them  at about the  
distance of the third part of an inch   
from the auricles of  the heart4 ,on    
bringing the opposite ends of these rods
 in contact with  each other1 the       
auricle first1 and then the ventricle of
 the heart  immediately contracted1 and 
repeated their contractions as often as 
the  ends of the metal rods were made to
 touch each other4 ,when a stick of     
glass1 wax1 or wood1 was made use of in 
place of one of the metals1 no          
contraction took place4 ,contractions1  
however1 were excited by  irritating the
 heart itself with the point of a sharp 
instrument4 ,the  contractions were both
 more vigorous1 and more constant when  
the metals  were placed in contact with 
the heart itself1 than when touching    
only  its blood vessels and nerves4 ,i  
have several times attempted to trace   

some of the nerves1 which may be seen   
near the large blood vessels of  the    
heart of a frog1 into the heart itself1 
in order to arm them  separated from    
other parts2 but1 partly on account of  
their minuteness1  and partly on account
 of the weak state of my eyes1 which    
does not  permit me to look intently at 
minute objects1 ,i have never been able 
to  succeed4    ,since making this last 
experiment1 ,i have repeated it upwards 
of twenty  times4 ,in order to its      
complete success1 it is necessary that  
the  spontaneous contractions of the    
heart should nearly1 if not altogether1 
have ceased2 and1 when in this state1   
the experiment is rendered still  more  
satisfactory by removing the heart from 
the body of the frog1 and  laying it    
upon a plate of zinc4 ,we are then sure 
that its contractions  cannot have been 
excited1 by any mechanical irritation1  
arising from  the contractions of the   
muscles of the thorax4    ,for want of  
sufficient leisure1 and convenient      

opportunities1 ,i have  neglected to    
make this experiment upon any animals of
 warm blood1  except cats and rabbits4  
,a few days after ,i had discovered the 
possibility of exciting the heart to    
contraction by means of zinc1 and       
silver applied to its nerves1 ,i        
procured an ordinary sized cat1 and     
drowned it in water1 as nearly as       
possible1 of its own temperature4  ,four
 minutes after immersion1 it was taken  
out of the water and dryed4  ,its thorax
 was immediately laid open1 but no      
contractions were observed  in any part 
of its heart1 except in the right       
auricle1 and even these  were very      
slight4 ,a plate of zinc was then placed
 in contact with the  parvagum1 and     
intercostal nerves1 on one side of the  
trachea1 and a  half crown piece in     
contact with those of the other2 both at
 the  distance of about one third of an 
inch from the auricles4 ,every time  the
 zinc and silver were brought into      
contact1 complete contractions of  the  

right auricle1 and sometimes slight ones
 of the left were produced1  but none in
 the ventricles4 ,the contractions were 
observed to become  stronger1 in        
proportion as the metals were approached
 to the heart1 and  were strongest when 
one or both was in contact with the     
auricle4 ,i  think the contractions were
 fully as strong when molybdena1 as when
  silver was used4 ,no contractions     
could be excited1 by arming any of the  
nerves of voluntary muscles1 in this    
cat4    ,the next experiment was made   
upon a female cat1 far gone with young4 
,she was drowned in very cold water1 and
 although her thorax was opened  the    
instant she had ceased to struggle1     
which was in less than four  minutes    
after immersion1 her heart had ceased to
 contract2 nor could  its contractions  
be renewed1 either by the application of
 the metals in  the way described1 in   
the last experiment1 or by pricking or  
otherwise  irritating its surface3 but  
the diaphragm1 the intercostal muscles1 

the  fore legs1 and the ears1 continued 
to contract long and vigorously1  when  
the metals were as usual applied to     
their nerves4 ,on cutting into  the     
uterus1 however1 and taking out one of  
the young1 ,i found both  auricles and  
ventricles of its heart1 contracting    
most vigorously1  though the mother had 
now been dead upwards of twenty minutes4
    ,an opportunity1 not to be          
neglected1 now presented itself1 of     
trying if  it were possible to transmit 
this influence from the mother to the   
ftus1 through the medium of the         
umbilical chord4 ,i therefore applied   
the two metals in the manner ,i before  
described1 #ast1 to the uterus of  the  
mother1 and to the cotyledans2          
afterwards to several different  parts  
of her2 but neither uterus nor ftus were
 in any instance  affected4 ,as little  
was the ftus affected1 by arming the    
chord itself4  ,as the hearts of the    
kittens continued their spontaneous     
contractions1  for more than an hour    

after they were taken from the mother1  
,i had  repeatedly the pleasure of      
observing1 and pointing out to ,mr      
,thomson1  and ,mr ,simpson1 who        
obligingly lent me their assistance in  
these  experiments1 the effects of the  
metals when in contact with the         
parvagum1 and entercostal nerves1 both  
of quickening the repetition of  the    
hearts contractions1 while they         
continued spontaneous1 and of  exciting 
them anew when they had ceased to be so4
 ,this experiment1  repeated upon a     
kitten a few days after birth1          
succeeded1 but not quite  in so         
satisfactory a manner as the foregoing1 
although the heart  continued           
contracting for more than an hour and an
 half after the  thorax was opened4 ,its
 contractions were quickened1 and       
rendered  vibratory by the slightest    
mechanical touch of its surface2 so that
 it  was difficult to determine the     
precise share which the application of  
the metals had in their production4     

,when these had ceased1 ,i did not find 
that ,i could revive them by the        
application of the metals4 ,in the      
hearts of some young rabbits1 upon      
which ,i tried this experiment1 the     
contractions appeared to be still  more 
decidedly1 occasioned by the application
 of the metals1 than even  in the cats4 
,having ascertained this important fact1
 that one muscle1 not subjected  to the 
influence of the will1 might be made to 
contract by the  application of zinc and
 silver to its nerves2 ,i proceeded to  
examine  whether the same were the case 
with respect to all involuntary muscles4
  ,i could not1 however1 observe that   
any contractions were produced in  the  
stomach or intestines1 by placing the   
metals near the stomachic  flexus and   
semilunar ganglion in a cat4 ,i next    
proceeded to examine the  effects of the
 metals upon the different organs of    
sense4    ,m4 ,volta's discovery of the 
sensation produced upon the end of the  
tongue1 by coating its upper and under  

surfaces with different metals1  led me 
to compare this sensation with that     
produced by electricity4 ,i  found a    
very considerable difference between    
them4 ,both1 indeed1 are  subacid1 but  
as unlike to each other1 as the taste of
 vinegar is to  that of diluted         
vitriolic acid4 ,that occasioned by the 
metals is  accompanied with what is     
familiarly called the metallic taste2   
and  differs according to the metals    
employed4 ,with the greater number of   
metals it is scarcely perceptible4 ,with
 zinc and gold1 ,i think1 it is         
strongest2 next so with zinc and silver1
 or molybdena1 and insufferably         
disagreeable with any of them4    ,the  
sensation is most distinct when the     
tongue is of its ordinary  temperature1 
and when the metals are of the same     
temperature with the  tongue4 ,when     
either the tongue1 or the metals1 or    
both1 are heated or  cooled1 as far as  
can be borne without inconvenience1     
scarcely any  sensation is produced4    

,that this difference in the effect is  
owing to  the alteration which has been 
produced in the state of the tongue1 and
  not to that in the temperature of the 
metals1 is evident from  experiments    
which ,i have already related2 from     
which it appears that  neither the      
conducting1 nor the exciting powers of  
metals are affected  by differences of  
their temperature4 ,but ,i have found it
 the uniform  result of many            
experiments1 that both the life and     
irritability of the  most vigorous frogs
 is completely destroyed in a few       
minutes1 by  placing them in water      
heated to #ajf degrees of ,fahrenheit's 
scale4    ,cold1 however1 though it     
appears to affect the sensibility of the
  tongue nearly as much as heat1 did    
not1 in one or two instances in  which  
,i tried it1 affect the irritability of 
the muscles of a frog4  ,some separated 
legs contracted equally well after they 
had lain upon a  piece of ice for some  
hours1 as they did before they had been 

in that  situation4    ,whatever has a  
tendency to blunt the sensibility of the
 tongue1 as  laudanum1 a strong solution
 of opium in water1 distilled spirits1  
acids1 c4 diminishes the effect of the  
metals4 ,acids1 ,i think1  diminish it  
least4    ,on placing different metals  
in the meatus auditorius externus of    
both  my ears1 and establishing an      
insulated metallic communication between
  them1 ,i felt1 or fancied that ,i     
felt1 a disagreeable jirk of my head4   
,the metals used were a silver probe1 a 
roll of tin-foil1 and a common  brass   
conductor belonging to an electrical    
machine4 ,on withdrawing them  from my  
ears1 ,i experienced a feeling similar  
to that which one has  after emerging   
from under water4 ,i was not sensible of
 having hurt my  ears by the experiment1
 nor had ,i any uneasy sensation after  
it2 but1  on getting out of bed next    
morning1 ,i perceived both my pillow and
 my  face stained with blood2 and1 on   
examining1 found that it had come from  

one of my ears4 ,an hmorrhagy from this 
part had never happened to me  before4  
,from whatever cause this accident      
happened1 7and it is highly  probable   
that it arose from some hurt unperceived
 at the time71 ,i need  not say1 that ,i
 have never repeated the experiment1 and
 that ,i  certainly never shall4    ,i  
never could perceive1 that the senses1  
either of touch or of smell1  were in   
the least affected by the metals2 but   
the effect which they  produce upon the 
eye is very remarkable4 ,having laid a  
piece of  tin-foil upon the point of my 
tongue1 ,i placed the rounded end of a  
silver pencil-case1 against the ball of 
my eye1 in the inner canthus1  and      
suffered them to remain in these        
situations till the parts were so  far  
accustomed to them1 that ,i could       
examine the sensations produced2 ,i     
then brought the metals into contact    
with each other1 and1 to my  surprise1  
perceived a pale flash of light diffuse 
itself over the whole  of my eye4 ,my   

tongue was at the same time affected    
with a similar  sensation to that       
produced when both the metals are in    
contact with it4  ,on darkening the     
room1 the flash became more distinct1   
and of a  stronger colour4 ,this        
sensation is not the effect of pressure 
upon the  eye1 as in ,sir ,isaac        
,newton's experiment2 for no pressure   
should be  used4 ,all that is required1 
is1 that the silver lie between the lids
 of  the eye1 and in contact with any   
part of the ball4 ,if the experiment be 
made with zinc and gold1 instead of     
tin-foil and silver1 the flash is       
incomparably more vivid4 ,i had the     
disagreeable opportunity of trying  this
 experiment upon one of my eyes1 in a   
state of inflammation2 and1  in this    
case1 found the flash much more strong  
than it was in the  uninflamed eye4 ,i  
tried it likewise upon a patient1       
affected with  amaurosis2 but the man   
was so stupid that ,i could not satisfy 
myself as  to the precise result4       

,recollecting that fine nervous twigs   
pass from the ciliary or  ophthalmic    
ganglion1 through the sclerotic coat of 
the eye1 to the  choroid coat1 and to   
the uvea2 and that this ganglion is in  
great part  formed from a twig of the   
nasal branch1 of the fifth pair of      
nerves1 in  conjunction with a branch of
 the third1 ,i proceeded to try if1 by  
insinuating a rod of silver1 as far as  
possible1 up my nose1 and thus  arming  
this nasal branch1 ,i could1 by bringing
 the silver into contact  with a piece  
of zinc1 placed upon my tongue1 pass    
this new influence up  the course of the
 nerve1 and thus produce the flash in   
the eye4 ,the  experiment answered my   
most sanguine expectation4 ,the flash1  
in this  way produced1 is1 ,i think1 if 
any thing1 stronger than when the ball  
of  the eye itself is armed4 ,i now     
thought ,i had discovered a certain     
method1 by which ,i could ascertain the 
effect of ,galvani's influence1  upon a 
very important1 involuntary muscle1 the 

human iris4 ,it occurred  to me that the
 ingenious physiologist ,dr ,whytt1 had 
been able1 through  the medium of the   
nasal branch of the fifth pair of       
nerves1 to produce1  at pleasure1       
dilatations of the contracted pupil of a
 boy1 in the last  stage of             
hydrocephalus1 by applying aq4 ammonia  
to his nostrils2 and  this instance of  
the affection1 of an involuntary muscle1
 through the  medium of its nerves1 had1
 previously to making any experiments   
upon  the subject1 always operated with 
me as a strong presumptive argument1    
that the contractions of the heart might
 be influenced in a similar  manner4    
,i therefore desired some of my friends 
to observe my pupil1 while ,i  repeated 
the experiment1 which ,i have above     
described4 ,when the  external light was
 strong1 they found some difficulty in  
determining1  whether the pupil         
contracted or not2 but when no more     
light was  admitted1 than what was just 
sufficient for discerning the pupil1    

they  perceived a very distinct         
contraction1 every time the metals were 
brought into contact with each other4   
,this experiment requires some          
attention1 in order that it may succeed 
satisfactorily2 but although ,i  have   
repeated it a great number of times upon
 the eyes of others1 it  has seldom     
failed1 when made in a steady light1 and
 when the silver has  been passed far   
enough up the nose4    ,the dilatation  
of the pupil1 instead of its            
contraction1 on the  application of a   
stimulus to its nerves1 as in the case  
related by ,dr  ,whytt1 is1 ,i          
apprehend1 not so uncommon a            
circumstance1 as it may at  first be    
supposed4 ,i have myself seen three     
instances of it in diseases  of the     
head4 ,one of these was in an epileptic 
patient1 whose pupils1  during the      
intervals of his fits1 became suddenly  
dilated whenever his  eyes were exposed 
to a strong light4    ,my friend1 ,mr   
,george ,hunter of ,york1 while one day 

amusing himself with  repeating some of 
these experiments1 discovered that by   
placing one of  the metals as high up as
 possible between the gums and the upper
 lip1  and the other in a similar       
situation with respect to the under lip1
 a  flash was produced as vivid as that 
occasioned by passing one of the  metals
 up the nose1 and placing the other upon
 the tongue4 ,it differs1  however1 from
 the flash produced in any other way1 in
 the singular  circumstance of not being
 confined to the eye alone1 but         
appearing  diffused over the whole of   
the face4 ,on attending to the          
concomitant  sensations produced by this
 disposition of the metals1 ,i perceived
 that  a sense of warmth1 at the instant
 they were brought into contact1        
diffused itself over the whole upper    
surface of the tongue1 proceeding  from 
its root to the point4 ,dr ,rutherford1 
to whom ,mr ,hunter had  communicated   
this experiment1 remarked1 on repeating 
it1 that a flash  is produced not only  

at the instant the metals are brought   
into  contact1 but likewise at the      
instant of their separation4 ,while they
  remain in contact1 no flash is        
observed4    ,this fact is precisely    
analogous to one already mentioned of   
contractions being produced in the leg  
of a frog1 at the instant one of  the   
metals in contact with the other metal  
is withdrawn from the leg4    ,after    
this full detail of these curious       
phenomena1 ,i hardly need  remark1 that 
they demonstrate the free communication1
 which subsists  between the several    
branches of the fifth pair of nerves1   
and  consequently give strong support1  
if not absolute confirmation1 to the    
well known doctrine of nervous sympathy1
 or of the reciprocal  influence1 which 
different parts exert upon each other1  
through the  medium of nerves4    ,if ,i
 might be allowed to hazard a           
conjecture1 where we cannot have        
recourse to demonstration1 ,i should say
 that the flash1 observed in the  above 

experiments1 was the effect of          
contractions excited in  involuntary    
muscles by the application of a stimulus
 to their nerves2  or1 in other words1  
that the effects of the application of  
the metals  to the nasal branch of the  
first division of the fifth pair of     
nerves1  had been propagated through the
 ciliary ganglion1 along the ciliary    
nerves1 and to the choroid coat1 whose  
vessels it had excited into             
instantaneous action2 and that their    
action again 7as in the case of  action 
excited by pressure1 or a blow upon the 
eye17 had by stimulating  the retina    
occasioned the sense of light4    ,this 
supposition is1 ,i think1 rendered      
probable by several  considerations4 ,i 
have already shewn that this influence  
can excite  contractions in involuntary 
muscles1 through the medium of their    
nerves4 ,and certainly no reason can be 
assigned1 a priori1 why it  should not  
act equally upon every description of   
involuntary muscles2  upon those which  

make a part of the minutest vessels in  
the body1 as  well as upon the heart1 or
 upon the iris4    ,that it excites to  
increased action the arteries of the    
tongue in the  experiment1 in which a   
sense of warmth is produced along its   
surface by  the application of the      
metals to the lips1 seems to be almost  
demonstrated2 for it would be difficult 
to point out the presence of  another   
cause competent to occasion the         
evolution of the heat1 in this  case1   
besides the increased action of the     
arteries3 and that this cause  is       
competent to the effect we know from    
numberless experiments1 too  familiar to
 need being particularized here4        
,whether the metals1 however1 do or do  
not affect the action of the  blood     
vessels1 is a question which admits of  
solution by experiment4  ,the following1
 ,i confess1 was not quite satisfactory1
 and ,i have not  yet found leisure and 
opportunity to repeat it with all the   
attention  it requires4    ,i inspected 

the foot of a living frog with a        
microscope of very high  powers4 ,in    
fixing the foot so as to keep the web   
expanded1 a  considerable degree of     
inflammation was excited1               
notwithstanding every  precaution to    
avoid it4 ,the current of blood was seen
 distinctly in  several vessels1 now    
flowing rapidly1 now slowly1 and now in 
a  direction contrary to that in which  
it was first observed1 but with  equal  
rapidity4 ,a thin plate of zinc was     
introduced between the fleshy  part of  
the foot and its supporter1 and a silver
 probe was used as an  excitor4 ,to me1 
the circulation appeared very decidedly 
to be quickened  several times when the 
metals were made to touch each other3   
but the  gentlemen who assisted me could
 observe no change4 ,to prevent the     
contractions in the muscles of the leg  
from producing any fallacy1 the  crural 
artery should be laid bare1 and         
insulated from surrounding  parts1 by   
passing a thin plate of glass1 or       

sealing wax1 between it and  them4      
,that the flash is the effect of such an
 increased action of the  vessels1      
composing the choroid coat1 might be    
somewhat more difficult  to prove4 ,it  
is however known to every one1 that a   
blow1 and that  pressure upon the eye1  
are capable1 as ,i have before observed1
 of  producing a similar effect4 ,and   
the following case1 which ,bonetus      
quotes from ,hermannus ,cummius1 if it  
may be credited1 affords an almost      
positive proof1 that vision depends upon
 the stimulus given to the  retina by   
the activity of blood vessels in some   
part of the eye4  #8,quando theologus1  
plaga dolorifica1 a rupta instrumenti   
musici chorda  accepta1 nocte           
subsequenti jam adulta1 e somno         
evigilans1 cuncta clare1  ac si de die  
esset1 vidit1 adeo1 ut minimos          
picturarum et tapetum  tractus          
observare1 characteresque ex libro      
legere posset4 ,oculo vero  lso clauso1 
tenebras densissimas adesse ille        

percepit1 eodemque iterum  aperto1      
conclave illustratum visum est1 lucem   
tamen candel allatae  solisque          
splendorem de die1 gre tulit oculus     
affectus1 quod per  aliquot dies        
duravit1 tandemque sensim remisit4'     
,haller speaks of such cases as by no   
means uncommon1 and quotes the  names of
 several authors1 who have related      
similar ones4    ,the direction of this 
influence1 when suffered to pursue its  
natural  course1 appears to be the same 
with that of most other stimuli1 i4 e4  
from the place at which it first affects
 a nerve1 onwards to the part1  in which
 that nerve terminates4 ,i have         
repeatedly caused electrical  sparks to 
be passed into my own ulnar nerve at its
 passage over the  inner condyle of the 
humerus1 but both the sensations and the
  contractions produced by them have    
been entirely confined to the hand  and 
fore arm4    ,it appears too1 both from 
the experiments of ,dr ,monro1 and of   
,dr  ,william ,alexander of ,halifax in 

,yorkshire1 that when no communication  
is left between the trunk and posterior 
extremities of a frog1 except  by its   
sciatic nerves1 a strong solution of    
opium1 injected under the  skin of its  
posterior extremities1 deprives them    
both of their  sensibility and of their 
contractile power2 but that it does not 
in the  least affect the trunk of the   
body4 ,if1 on the contrary1 it be       
applied  to the trunk1 it exhausts both 
the trunk and the extremities4    ,m4   
,galvani is said to have observed the   
effects of the influence1 which  he     
discovered1 diffused over the whole body
 of a frog1 when the metals  were       
applied to a nerve merely laid bare1    
without being either divided  or        
separated from surrounding parts4 ,if we
 are allowed to infer this  diffusion of
 the influence from the restlessness    
expressed by the  animal1 ,m4 ,galvani's
 observation may be just4 ,if from the  
contractions  produced1 ,i suspect it is
 by no means so2 since1 in every        

experiment  which ,i have made upon the 
subject1 the contractions have been     
confined  to those parts to which the   
nerve touched by the metals was         
distributed4    ,that this influence1   
however1 may pass in a direction        
contrary to the  course of nerves1 is   
evident from some of the experiments    
which ,i have  related relative to its  
effects upon the senses1 but is still   
more  clearly demonstrated by the       
following4    ,if1 after having divided 
at the pelvis a frog recently killed1   
the  sciatic nerves be freed from       
cellular membrane up to their origin    
from  the spine1 and all the parts below
 this1 except themselves1 be cut  away1 
the muscles on each side of the spine1  
for some little way up1  may be brought 
into contraction by touching the nerves 
alone with the  two metals in contact4  
,this experiment has not always         
succeeded with  me1 and never unless the
 frog had been recently killed4 ,so long
 as the  hind legs remain undivided from

 the nerves1 it never succeeded2 the    
only contractions produced being in the 
legs4                               ,,of
 ,,the ,,blood ,,vessels4    ,we are    
told by ,dr ,valli1 that no contractions
 are excited by arming the  blood       
vessels2 but as he has not told us      
whether his experiments were  made upon 
them while the blood still continued to 
flow through them1 or  after they had   
been deprived of their blood1 ,i        
determined to make the  following       
experiment4    ,having laid bare1 and   
separated from surrounding parts and    
from each  other1 the crural artery1 and
 nerve1 in the thigh of a full grown    
frog1  ,i cut out the whole of the nerve
 between the pelvis and the knee4 ,i    
then insinuated beneath the artery a    
thin plate of sealing wax1 spread  upon 
paper1 and broad enough to keep a large 
portion of the artery  completely apart 
from the rest of the thigh4 ,the blood  
still continued  to flow1 through the   
whole course of the artery1 in an       

undiminished  stream4 ,the artery1 thus 
partially insulated1 was touched with   
silver  and zinc1 which were then       
brought into contact with each other2   
but no  contraction whatever was        
produced1 in any muscle of the limb4    
,this  experiment was frequently        
repeated upon several different frogs1  
both  in whom the nerve was1 and in whom
 it was not1 divided4 ,the result was   
uniformly the same4 ,but vivid          
contractions were produced in the whole 
limb1 when an electrical spark1 or even 
a full stream of the aura1 was  passed  
into the artery4    ,it1 however1 by no 
means follows from this experiment1 that
 the  sanguiferous system of animals    
bears no relation whatever to the       
influence discovered by ,galvani4 ,i    
have already shewn1 that the heart  may 
be affected by it1 and have given reason
 to believe1 that the  smallest arteries
 of the body are not exempted from its  
action4 ,should  it ever be proved to be
 an exclusive property of animals1 it is

 not  impossible but that even its      
origin may be traced to their           
sanguiferous  system4    -----          
,footnote #aa3      ,i have not been at 
the pains to inform myself1 who first   
was the    author of this doctrine2 but 
its adoption by ,caldani1 by ,haller1   
and    by ,fontana1 and by all upon the 
faith of experiment1 was certainly      
sufficient to give it currency1 in      
opposition to that of ,willis1          
,lower1 ,kaau1 ,boerhaave1 ,laghi1 and  
even of the ingenious ,whytt4           
,footnote #ab3      ,mem4 ,med4 ,soc4   
,lond4 vol4 iii4                        
----------------------------------------
--------------------------------        
,,section ,,iv4        ,an attempt to   
investigate the ,source from which the  
respective              ,powers of      
,nerves1 and of ,muscles1 are derived4  
,as yet1 the question whence the nerves 
and muscles of animals derive  their    
respective properties1 remains in a     
state of doubt4 ,by many1 the  brain has

 been considered as the source not only 
of the several  energies exerted by     
nerves1 whether appropriated to         
sensation1 to the  excitement of muscles
 subservient to the will1 or distributed
 to organs  exempted from its influence2
 but likewise of that unascertained     
power1  by which muscles contract on the
 application of a stimulus4    ,by      
others again1 these several properties  
are supposed to be derived  from the    
arteries1 which may either supply the   
materials and  construction of that     
exquisite and peculiar organization1    
which fits  nerves and muscles for      
performing their respective functions1  
or may  furnish1 from the blood1 some   
subtile principle1 such as that believed
  by ,m4 ,fontana1 to exist there1 or   
such as that we are now examining1      
which differently modified in different 
parts1 may be the latent cause  of all  
the phenomena exhibited by animals4     
,the advocates for the first opinion    
observe1 that whenever the brain is     

considerably injured1 or its free       
communication1 by means of nerves1  with
 moving parts is interrupted1 a         
deprivation both of sense and  motion is
 the uniform consequence3 and1 further1 
that the several  organs1 both of sense 
and of motion1 appear to suffer         
detriment from  the over strained       
exertions of the brain in thinking1     
equal to that  which they experience    
from their own exertions4    ,the second
 opinion is countenanced by facts and   
observations not less  important4 ,from 
experiments of ,haller2 some which are  
recorded in one  of the early volumes of
 the ,philosophical ,transactions1 and  
others1 it  appears that a paralysis of 
the posterior extremities of animals was
  induced by tying their aorta4    ,both
 ,dr ,monro and ,dr ,alexander of       
,halifax have remarked1 that when all   
the blood vessels1 supplying the        
posterior extremities of frogs1 had     
been divided1 and a solution of opium   
injected under the skin of these        

extremities1 they became1 in less than  
half an hour1 both motionless  and      
insensible2 whereas1 the fore part of   
the body was not observably  affected   
six hours afterwards2 and1 in ,dr       
,monro's experiments1 the  frogs lived  
till the day following4 ,hence ,dr      
,monro concludes1 #8that  concomitant   
arteries1 somehow or other1 tune the    
nerves1 so as to fit  them to convey    
impression#ac4'    ,on the other hand1  
where it is intended that nerves shall  
convey  impressions with great accuracy1
 as in all the senses1 and very         
remarkably in the part which some have  
amused themselves by considering  as a  
sixth organ of sense1 the distribution  
of blood vessels is more  profuse than  
in almost any other equal part4 ,it is  
likewise universally  true1 that        
increase of vascular action in a part is
 always attended  with a proportional   
increase of sensibility there4    ,from 
the valuable experiments made by ,mr    
,cruikshanks1 and which have  since     

received the fullest confirmation from  
those repeated by ,m4  ,fontana and     
others1 it appears1 that whatever may be
 the relation  between brain and nerves1
 the latter may certainly be regenerated
 after  excision1 and have their        
functions fully restored4 ,now1 in what 
manner  this can be accomplished1 unless
 by the agency of arteries1 would1 ,i   
imagine1 be no easy task to point out4  
,the influence discovered by ,galvani   
appeared to me an admirable test1  by   
which something decisive might be       
ascertained relative to these  important
 points in the physiology of animals1   
and as such ,i have  employed it in the 
following experiments4    ,considering1 
therefore1 the brain on the one hand1   
and the sanguiferous  system on the     
other1 as the possible sources from     
which nerves and  muscles might derive  
their power1 ,i began by comparing the  
effects  which result from interrupting 
their communication1 first with the     
brain1 and then with the arteries4 ,this

 mode of procedure seemed to  afford the
 best prospect of information with      
respect to every object  which ,i had in
 view1 but particularly with regard to  
the relations  which this influence may 
bear to the several parts examined4     
,before relating the experiments1 ,i    
must observe that the comparison was    
instituted between the effects of only  
partially interrupted  communication2   
since it must be obvious that a complete
 interruption1  either of nervous or of 
arterious communication between any part
 of an  animal1 and the rest of its     
body1 could not have been effected      
without  so far injuring the animal1 as 
to render the result fallacious4        
,experiments in which the ,sciatic      
,nerves of ,frogs were divided4         
,,experiment ,i4    ,i divided the      
sciatic nerve1 on one side only1 in four
 large frogs4 ,the  division was made at
 the very top of their thighs1 and      
before the nerve  had given off the     
first large branch to the muscles of the

 thigh4 ,this  nerve lies immediately   
underneath the large crural artery1 to  
which it  is closely attached by a      
sheath of fine but very strong cellular 
membrane4 ,a small nerve1 which supplies
 some of the muscles on the  under side 
of the thigh1 was suffered to remain    
undivided4 ,the legs1  whose nerves had 
been divided1 became completely         
paralytic below the  knee1 and very     
nearly so above it4 ,these legs too1    
immediately after  the division of their
 nerves1 contracted vigorously when laid
 upon  zinc1 and excited by passing a   
rod of silver in contact with the under 
part of the knee till it touched the    
zinc2 but the other legs which  were    
suffered to remain in their natural     
state1 in order that the  contractility 
of one leg might all along be compared  
with that of the  other1 did not        
contract when the metals were similarly 
applied to them4    ,these frogs were   
all killed by cutting off their heads2  
the first1 at  the end of two days after

 dividing the nerve2 the second1 at the 
end of  five days2 the third1 at the end
 of seven2 and the fourth1 at the end   
of nine4 ,their legs were carefully     
examined1 in the manner ,i have         
described1 four or five times every day 
after their heads had been  taken off1  
so long as any contractions could be    
excited2 but ,i could  not perceive1 in 
any one of these instances1 that the    
contractile power  continued either     
longer or more vigorous in the legs1 in 
which the  nerves were not divided than 
it did in those in which they were4     
,both in these experiments1 and in all  
my others1 where a comparison was       
instituted between the two legs of the  
same frog1 ,i divided equal  portions of
 skin on both thighs1 that there might  
be no unequal  exposure of the muscles  
to the water1 which would have          
occasioned a  fallacy in the result4    
,,experiment ,,ii4    ,on the #cast of  
,march last1 ,i divided1 in two1 a frog1
 in one of whose  legs ,i had four      

months before excited inflammation1 by  
laying bare the  crural artery and      
nerve4 ,the inflammation had been so    
violent and  general1 that the frog lost
 its cuticle in consequence of it1 and1 
when  compared with a healthy frog1 its 
resperation was observed to be          
remarkably frequent4 ,three weeks after 
this1 when the wound in its  thigh had  
perfectly skinned over1 ,i laid it open 
again1 and divided the  sciatic nerve4  
,no general inflammation this time took 
place1 nor did  the wound again skin    
over2 but for about a month before it   
was killed1  a large ulcer had formed   
immediately over the division of the    
nerve1  but had not proceeded down to   
it4 ,the limb1 at the time ,i killed the
  frog1 was as destitute both of motion 
and of sensation1 as at the first       
instant the nerve was divided1 but      
contractions were excited in it1 by     
touching the ulcer with zinc and silver4
 ,when the frog was dead1  however1 the 
contractions were found much more feeble

 in this than in  the other leg4    ,the
 metals were now applied to the sciatic 
nerves within the abdomen4  ,vigorous   
contractions were excited in the sound  
leg1 but none in that  whose nerve had  
been divided4 ,hence it was plain1 that 
no actual  regeneration had taken place4
 ,on examining the nerve accurately at  
the  part divided1 ,i found the divided 
ends1 which had receded considerably    
from each other1 connected by a         
transparent gelatinous substance4 ,from 
the upper end1 which appeared elongated 
into a conical form1 several  red       
streaks projected into the interposed   
substance4 ,the lower end was  opaque1  
thickened1 and rounded4 ,no appearance  
of spiral bands could be  detected1     
either in the interposed substance1 or  
in the part of the  nerve below the     
division1 when these parts were examined
 with the  assistance of a microscope4  
,this substance had attained sufficient 
consistence to support the under part of
 the nerve1 when the upper was  raised  

with a pair of forceps4 ,the leg1 in    
which the nerve had been  divided1      
continued to contract as long as the    
other1 though much less  vigorously1 and
 the part1 from which ,i could longest  
excite  contractions1 was the ulcer4    
,,experiment ,,iii4    ,on the #adth of 
,april last1 ,i killed two other frogs1 
by dividing their  hind extremities from
 their bodies4 ,in one1 the right       
sciatic nerve had  been divided more    
than six weeks previous to its death4   
,in the other1  one of the sciatic      
nerves had been divided between three   
weeks and a  month4    ,the legs of     
these frogs1 examined by the metals both
 before and after  their separation from
 the body1 were found in a state very   
different  from those before spoken of4 
,the contractions were scarcely         
perceptible4 ,the incisions made through
 the skin1 in order to get at  their    
nerves1 had closed completely in less   
than a week after they had  been made4  
,the appearance of the muscles in the   

legs1 whose nerves had been  divided1   
was found to be precisely the same as in
 those where nothing  had been done2    
but1 notwithstanding this circumstance1 
even strong  electrical sparks excited  
but very feeble contractions4 ,on       
examining  the nerves1 the ends of that 
which had been longest divided were     
found  connected by a substance not at  
all resembling nerve1 but similar to    
that found in the former experiment1 and
 evidently proceeding from the  upper   
division4 ,in the nerve which had not   
been so long divided1 this  circumstance
 was still more apparent1 as the        
substance had not extended  quite to the
 lower division4 ,the cellular membrane 
surrounding these  upper divisions had  
the appearance of innumerable vessels   
finely  injected1 and some red streaks  
were seen projecting1 as if from the    
nerve itself1 into the gelatinous       
production4 ,in the sound nerves1 the   
obliquely transverse lines of alternate 
opacity and transparency1 or1  as       

,fontana has called them1 the white     
spiral bands of nerves1 were seen       
distinctly at the first glance of the   
eye1 and without the assistance  of a   
glass2 but no appearance of these could 
be found in the parts of  the divided   
nerves below the division2 these were   
uniformly opaque4  ,their bulk1 however1
 was not in the least diminished4 ,the  
organization  of nerves long divided1   
therefore1 undergoes a very evident     
alteration1  although it is by no means 
so clear that the same change happens in
 the  muscles1 to which these nerves are
 distributed4 ,yet their  susceptibility
 to the action of electricity1 as well  
as to that of this  new influence1 was  
nearly lost4 ,some may consider this as 
an additional  argument1 that stimuli   
act upon muscles only through the medium
 of  nerves4    ,i have before observed 
that muscles of frogs1 from whom the    
skin has  been stripped1 become in a    
short time hard when exposed to the     
action  of water4 ,wishing1 therefore1  

to see if there would be any difference 
between these legs1 whose nerves had    
been divided1 and others1 in this       
respect1 ,i laid them in water1 and     
examined them every ten minutes1 but    
both became hard nearly at the same     
time4 ,mr ,allen1 a gentleman well      
versed in physiological pursuits1 was   
with me when ,i examined the  alteration
 which had taken place in one of these  
nerves1 in consequence  of its having   
remained long divided1 and ,i had       
afterwards an  opportunity of shewing it
 to ,dr ,rutherford4 ,in all the frogs1 
whose  nerves ,i have divided1 ,i have  
observed that the divided extremities1  
though placed in most exact contact from
 each other1 had after a time  receded  
at least #a_/ab of an inch from each    
other4                 ,experiments in  
which the ,crural ,arteries of ,frogs   
were tied as near to the ,trunks of     
their ,bodies1      as where the ,nerves
 had been divided in the former         
,experiments4                           

,,experiment ,i4    ,both crural        
arteries of a full grown frog having    
been laid bare1 one of  them was tied4  
,the leg1 in which this was done1 became
 instantly weaker  than the other1 and  
rather dragged when the animal was put  
into water4  ,the frog1 however1 could  
still jump about with great agility4    
,four  hours after this operation1 it   
was killed by crushing its brain4 ,it   
continued to move its legs              
spontaneously1 when touched1 during more
  than two days after this1 and         
contractions were excitable by the      
application of the metals for two days  
longer4 ,sometimes it appeared  rather  
doubtful1 which leg contracted most     
vigorously1 but1 in general1  the leg in
 which the artery remained free did so1 
and contractions  could be excited in   
it1 more than an hour after every means 
to excite  them in the other leg had    
failed4                                 
,,experiment ,,ii4    ,ligatures were   
passed round the crural arteries of two 

other frogs1 and  one of them was       
suffered to live thirty six hours       
afterwards1 before  its head was        
crushed3 the other four days4 ,in these1
 the disproportion  between the vigour  
and continuance of the contractions in  
the compared  legs1 was so much greater 
than in the preceding experiment1 as to 
leave  no doubt of the effects produced 
by tying an artery4 ,the leg1 whose     
artery had remained tied four days1     
never contracted near so strongly  as   
its fellow1 and contractions had ceased 
to be excitable in it1  upwards of      
twenty hours before they had ceased in  
the leg1 whose artery  had not been     
tied4    ,from these experiments1 it    
appears decidedly1 that a much greater  
detriment to that condition of a limb1  
upon which contraction depends1  is     
induced by interrupting its circulation1
 than by intercepting its  communication
 with the brain4    ,but still1 as the  
effects arising from the interception of
 the  influence of the brain1 and of the

 circulation1 were not compared with    
each other in the same but in different 
animals1 whose age1 relative  strength1 
c4 might possibly differ1 ,i thought    
proper to repeat the  comparison1 in the
 following manner4          ,experiments
 in which the ,sciatic ,nerve was       
divided on one side1                 and
 the ,crural ,artery tied on the other4 
,,experiment ,i4    ,i divided the      
sciatic nerve of one leg1 and tied the  
crural artery of  the other1 in a large 
frog4 ,scarcely any blood was lost in   
doing  either4 ,two days after this1 ,i 
strangled it4 ,during the first #bd     
hours1  the leg1 in which the nerve had 
been divided1 appeared to contract with 
most vigour2 after this period1 the     
difference between them became more     
doubtful2 but the contractions were at  
no time stronger in the leg1  whose     
artery was tied1 than in that whose     
nerve was divided4                      
,,experiment ,,ii4    ,the same         
operations were performed upon a large  

female frog full of  spawn4 ,four hours 
afterwards1 she was observed covered by 
a male1 who  had been treated in a      
similar manner4 ,i mention this         
circumstance1 as  it tends to prove that
 the pain occasioned by the operation   
was  probably not so great as to produce
 much fallacy4    ,on the day following1
 she had spawned1 and on the sixth day  
from the  operations1 she was strangled4
 ,when laid upon a plate of zinc1 and   
excited by means of a rod of silver1 the
 contractions were found  extremely     
feeble in the leg whose artery had been 
tied1 and ceased  altogether in about   
twenty-two hours after her death4 ,in   
the leg1 whose  nerve had been divided1 
they appeared as vigorous as they       
usually are  in legs to which no injury 
has been previously done1 and continued 
excitable upwards of two days after they
 had ceased to be so in the  other4     
,,experiment ,,iii4    ,having tied the 
crural artery on one side1 and divided  
the sciatic  nerve on the other1 on     

three full grown male frogs1 ,i         
strangled them  all on the sixth day    
following4 ,my motive for killing the   
frogs1  subjected to such experiments1  
either in this manner or by crushing    
their heads1 will be obvious4 ,it was of
 consequence to preserve their          
circulation as entire as possible1 and1 
at the same time1 avoid the  continuance
 of pain1 which by exhausting all the   
parts of the body1  whose communication 
with the brain was not interrupted1     
might  considerably have affected the   
result of the experiments4    ,the      
contractions excited by means of the    
metals1 were1 in all these  instances1  
likewise as much more strong and durable
 in the legs1 whose  nerves had been    
divided1 than what they were in the     
legs1 whose  arteries had been tied1 as 
what ,i had found them to be in the     
preceding  experiment4    ,having thus  
found1 that a diminution of the         
circulation of a part1 was  accompanied 
with a proportionable diminution of the 

respective powers  of nerves and muscles
 in that part1 ,i next proceeded to     
examine if an  increased circulation    
would be attended with a proportionable 
increase  of these powers4 ,that this is
 actually the case1 with respect to the 
nerves1 the few facts which ,i have     
related of the eye1 in a state of       
inflammation1 have a tendency to prove2 
and we all know how much the            
sensibility of every part of the body is
 increased1 by an increase of  vascular 
action4 ,that a similar relation        
subsists between an increased  action of
 the arteries1 and the contractile power
 of muscles1 is1 ,i  think1 proved by   
the following experiment4               
,experiments made with a view of        
ascertaining                   some of  
the ,effects of ,inflammation4          
,,experiment ,i4    ,i have before said 
that if a living and entire frog be set 
upon a plate  of zinc1 contractions can 
very seldom be produced in any part of  
its  body by passing a rod of silver    

over it1 so that the silver1 the frog1  
and the zinc1 may be all in contact with
 each other4 ,but1 ,i have found  in    
upwards of twenty experiments1 that when
 inflammation had been  excited in one  
of the hind legs of a frog1 by          
irritating it with a  brush1            
contractions uniformly took place in    
that leg when the metals  were applied  
to it1 although none had been produced  
in it before it was  inflamed1 nor could
 still be produced in the other leg     
which remained  in its natural state4   
,,experiment ,,ii4    ,having previously
 excited inflammation1 by means of a    
brush1 in the  foot and leg of a healthy
 and large frog1 ,i cut off its head4   
,the  contractions excited by the metals
 in the inflamed leg were in vigorous   
and instantaneous jirks2 those in the   
sound leg more languid and  difficultly 
excited4 ,spontaneous motions continued 
at this time nearly  the same in both4  
,till the end of the second day1 after  
this frog's  head had been taken off1   

the contractions excited in the inflamed
 leg  continued uniformly1 and beyond   
all comparison more vigorous than what  
,i could by any means excite in the     
sound leg4 ,but1 after this time1 the   
inflamed leg became hard as a piece of  
wood2 probably in consequence of  the   
effusion to which the inflammation had  
given rise4    ,the event of five       
similar experiments was so nearly the   
same1 that ,i  should be thought        
unnecessarily minute1 were ,i to relate 
them in detail4    ,we are now perhaps  
prepared to account for the deficiency  
of  contractile power in those legs1    
whose sciatic nerves had been divided1  
the one1 between three weeks and a      
month1 the other1 six weeks1  compared  
with its continuance in the leg1 whose  
nerve had been divided  upwards of three
 months4 ,it appears1 from the          
circumstances of those  experiments1    
that some of the arteries1 appropriated 
to the supply of  the sciatic nerves of 
frogs1 have the same course with the    

nerves  themselves2 since the deposition
 of new matter could in all be traced   
from the upper division of the nerves4  
,it is obvious1 therefore1 that  the    
part of the nerves below the division1  
must have been deprived of  so          
considerable a portion of their usual   
arterial supply1 as in time  would      
occasion some alteration in their       
structure1 and consequently in  their   
powers4 ,we accordingly find that such  
alteration of structure1  and such      
deficiency of power1 had actually taken 
place4 ,it is further  probable1 that1  
in proportion as the supply from the    
arteries was  restored1 the powers of   
that nerve1 which had been three months 
divided1 had been likewise restored4    
,this supposition is countenanced  by   
every instance in which nerves are      
reproduced2 as we find the  functions of
 the parts in which they had been       
divided1 are not  immediately1 but      
gradually restored4    ,m4 ,fontana     
seems too hastily to have adopted the   

opinion1 that the  sciatic nerves1 when 
divided1 are probably never reunited by 
truly  nervous structure1 because no    
reunion took place during the very short
  period which he suffered to elapse    
between their division1 and their       
subsequent examination4 ,in the         
experiments1 which ,i have related1 the 
progress towards reunion seems to have  
borne a very exact proportion to  the   
time the nerves had remained divided2   
and1 in an experiment related  by ,dr   
,monro1 where the sciatic nerve of a    
frog had been divided a year  previous  
to the death of the animal1 the         
reproduction was advanced so  far as to 
have the appearance of being perfect4   
,nor can ,i doubt1 that  both the       
sensibility and the motion of the limb  
would have been  restored1 had the      
animal been permitted to live a         
sufficient length of  time4 ,the        
following fact renders the supposition  
at least extremely  probable4    ,in the
 first volume of the ,edinburgh ,medical

 ,essays1 the case of a  ,captain of a  
man of war is related1 who entirely lost
 the use of his  right arm1 in          
consequence of a gun-shot wound received
 in his neck4 ,the  circumstances of the
 case are such as leave no reason to    
doubt1 that  the loss of the power of   
motion1 in this gentleman's arm1 was    
owing to  the division of the cervical  
nerves proceeding to the arm3 yet both  
the  full use1 and strength of this arm1
 were restored1 after a period of  about
 two years and a half4 ,a proof         
perfectly satisfactory that an  actual  
regeneration of nerves had1 in this     
case1 taken place2 and if in  this1 one 
sees no reason why it should not equally
 take place in any  other part of the   
body4    ,it might be difficult to      
assign a satisfactory reason for the    
very  speedy reproduction of the        
intercostal1 parvagum1 and recurrent    
nerves1  when compared with the great   
length of time required for the         
reproduction of others4 ,may it not be  

owing to the very profuse manner  in    
which they are supplied with arteries1  
probably both in an  ascending1 and in a
 descending direction2 from above1 by   
the superior1  and from below1 by the   
inferior laryngeal arteries8    ,it     
appears upon the whole1 therefore1      
tolerably certain1 that the             
sanguiferous system contributes more    
immediately than the brain to the       
support of that condition of muscles and
 of nerves1 upon which the  phenomena of
 contraction depend2 since that         
condition is much more  injured by      
intercepting the influence of the former
 than of the latter4    ,every          
experiment and observation1 which has   
been made upon the subject  of          
nutrition1 and of the reproduction of   
parts1 clearly demonstrates  that nerves
 and muscles1 in common with every other
 part of the body1  derive their        
structure from the arteries2 and it is  
evident1 that upon  this structure their
 several properties must in some measure

 depend4  ,but ,m4 ,galvani's discovery 
of a subtile influence1 which may be    
transmitted apparently from one part of 
an animal to another through  foreign   
media1 may reasonably give rise to a    
conjecture that the  phenomena exhibited
 by nerves and by muscles may perhaps   
depend more  immediately upon some such 
influence2 and reasons exist1 which     
might  induce some to suspect that even 
this is derived from the blood4         
,experiments suggested by some opinions 
of ,m4 ,fontana4    ,from the greatest  
number of experiments1 perhaps1 ever    
made by one  physiologist1 ,m4 ,fontana 
has been led to conclude1 that the venom
 of  the viper1 opium1 and several other
 poisons1 which he examined1 produce  no
 effects whatever1 when applied         
immediately to nerves and muscles       
alone1 but that they destroy life1 by   
exerting their influence upon  some     
subtile principle existing in the blood4
    ,independent of the experiments1    
published by ,m4 ,fontana1 on this      

subject1 his opinion respecting the     
existence of such a principle may  be   
thought to receive no inconsiderable    
countenance1 from the opinions  of      
,harvey and of ,mr ,hunter1 concerning  
the life of the blood1 and from  those  
experiments1 by which ,mr ,hewson has   
demonstrated1 that changes  are         
instantaneously produced upon the       
coagulability of the blood1 by  passions
 of the mind1 and whatever else affects 
the action of the heart  and arteries4  
,an experiment made by ,dr ,alexander of
 ,halifax1 and  published at this place 
in the year #agij1 in his excellent     
,thesis1 #8,de  partibus corporis quae  
viribus opii parent1' may at first      
appear a  sufficient refutation of ,m4  
,fontana's opinion4    ,he found that   
thirty three drops of a strong solution 
of opium in  water1 injected into the   
jugular vein of a large rabbit1         
destroyed it1  as in ,m4 ,fontana's     
experiments1 in four minutes and a half2
 whereas1  the same quantity injected   

into the crural vein in each leg of     
another  rabbit1 with an interval of    
twenty six minutes between the two      
injections1 although it rendered the    
animal sleepy and stupid for a few      
hours1 did it no material or permanent  
injury4 ,hence1 ,dr ,alexander          
concludes1 that the opium1 injected into
 the jugular vein1 did not  destroy the 
animal by acting upon the blood alone1  
since if it had1 the  same effect1      
should have been produced1 by           
introducing an equal  quantity into any 
other vein of the body2 but a quantity  
double of  that1 which had occasioned   
death when introduced into the jugular  
vein1  failed to occasion it when       
introduced into the crurals4    ,it is  
not1 however1 by one experiment1        
formidable as it must be allowed  to be1
 that the innumerable hosts brought to  
the contest by ,m4 ,fontana  ought to be
 combated4 ,besides1 it might be        
objected even to this one1  that the    
opium was introduced into veins1 from   

which it must have been  so much longer 
in passing to the arterial blood1 than  
from the jugular  vein1 and consequently
 so much more diluted1 and perhaps too  
altered in  its nature before it got    
there1 as might be sufficient to account
 for  the difference of result in the   
two cases compared4    ,the opportunity 
afforded by ,m4 ,galvani's discovery1 of
 putting the  truth of the opinion held 
by ,m4 ,fontana more fully to the test1 
and the  possibility which presented    
itself1 that if any such principle1 as  
he  supposes in the blood1 should really
 be found to exist there1 it might      
prove to be identically the same with   
that discovered by ,m4 ,galvani1        
induced me to make the following        
experiments4                            
,,experiment ,i4    ,having selected two
 frogs as nearly as possible of the same
 size and  vigour1 ,i deprived one of   
its blood by opening1 first1 one of its 
crural veins1 then1 a crural artery1 and
 last of all1 the heart4 ,to  assure    

myself of the complete evacuation of its
 blood1 ,i next injected  water into its
 heart1 and immediately afterwards forty
 drops of a  strong aqueous solution of 
opium#ad4      ,i then removed the      
sternum of the other frog1 and having   
made an  opening into the ventricle of  
its heart1 injected into it likewise    
forty drops of the solution4 ,less blood
 was effused in doing this1 than  one   
would at first expect2 for the ventricle
 contracts so strongly1  immediately    
after the incision1 as to prevent much  
blood from passing  out1 unless the     
incision be made1 as it was in the other
 frog1  purposely large4    ,the moment1
 at which each injection was made1 was  
accurately noted1 and  the time expended
 in evacuating the blood from the first 
frog1 was  allowed for4 ,the frog1 from 
which the blood had been withdrawn1     
ceased  to contract1 when irritated1    
very nearly an hour before the other1   
even  calculating not from the time of  
injection1 but from the moment ,i began 

to bleed it2 nor could ,i by means of   
the metals excite contractions in  it1  
for upwards of a day before they had    
ceased to be excitable in the  other    
frog4                                   
,,experiment ,,ii4    ,as evacuating the
 blood from a living animal is rather a 
severe  operation1 and might have       
occasioned some fallacy in the last     
experiment1 by subjecting the frog1 in  
which this was done1 to a  greater      
degree of pain1 and consequently of     
exhaustion1 than what the  other was    
subjected to1 ,i crushed the brains of  
two other frogs before  ,i proceeded1 as
 in the former experiment1 to withdraw  
the blood from  one of them4 ,instead of
 forty1 ,i injected no more than        
thirteen drops  of the strong solution  
of opium1 into each of the hearts of    
these  frogs4 ,the instant the injection
 had entered1 both hearts became white1 
and ceased from contracting4 ,forty     
eight hours after the injection of  the 
opium1 the contractions excited by the  

metals in the frog1 deprived  of its    
blood1 had become very slight1          
particularly in the limb whose  vein and
 artery had been opened4 ,the other frog
 still continued to  contract with so   
much vigour1 as to raise its body from  
the plate of  zinc1 upon which it was   
laid4 ,seventy two hours after the      
injection1 no  contractions could be    
excited in the frog1 from which the     
blood had  been withdrawn1 except some  
very slight ones in the leg1 whose      
artery  and vein had not been opened4   
,the contractions in the legs of the    
other  frog1 continued still so vigorous
 as to raise its body from the plate1   
and some were produced even by          
mechanical irritation4    ,ninety six   
hours after the opium had been injected1
 7both the frogs  having lain out of    
water all night17 that without blood was
 found quite  putrid4 ,in the other1 the
 contractions1 produced by exciting the 
legs1  were sufficiently strong to move 
the feet3 as the body1 however1 had     

become putrid and offensive1 it was     
thrown away4                            
,,experiment ,,iii4    ,the heads of two
 other full grown and lively frogs1     
having been  crushed1 their hearts were 
laid bare1 and the blood was evacuated  
from  one of them1 as in the former     
experiments4 ,a small portion of the    
skull  of each then being removed1 eight
 drops of the strong solution of opium  
was injected upon their brains4 ,at     
least half the quantity seemed to       
return from the wound4 ,both frogs      
became instantaneously motionless  after
 the injection1 but1 in about an hour1  
were considerably recovered4            
,spontaneous motions continued during   
more than fifty hours1 in the legs  of  
that from which the blood had not been  
drawn1 and contractions were  excitable 
by the metals1 upwards of #bd hours     
after they had ceased to  be so1 in that
 from which the blood had been drawn4   
,the following experiments may be deemed
 still more satisfactory1 than  the     

preceding1 from the circumstance of the 
comparison having been  instituted1     
between the effects of opium1 upon      
different1 but similar  parts of the    
same frog1 differently circumstanced4   
,,experiment ,,iv4    ,one of the crural
 arteries of a frog having been included
 in a tight  ligature1 as near as       
possible to the body1 ,i suffered four  
days to  elapse1 and then injected      
through a perforation in its skull1     
eight  drops of the strong solution upon
 its brain1 and in a direction towards  
its spinal marrow4 ,this frog continued 
most violently convulsed for  more than 
an hour1 and1 in two1 was to all        
appearance dead4 ,when laid  upon zinc1 
and excited with silver1 the            
contractions were not at first          
perceptibly stronger in one leg than in 
the other4 ,after eight hours1  however1
 they were evidently most strong in the 
leg whose artery  remained free4 ,after 
#ba hours1 this difference became still 
more  decided4 ,at the end of #cd hours1

 scarcely any contractions could be     
excited in the leg whose artery had been
 tied2 though they continued  vigorous  
in the other2 and1 at the end of #df    
hours1 they had ceased  altogether to be
 excitable1 in the leg whose artery was 
tied4 ,in the  other1 they continued    
during several hours afterwards4        
,,experiment ,v4    ,having tied one of 
the crural arteries of another frog1 ,i 
filled its  stomach1 immediately        
afterwards1 with a saturated solution of
 opium in  water4 ,the difference       
between the strength1 and the           
continuance of the  contractions1       
excited by the metals1 in the two legs  
of this frog1 was  not so great as in   
the former2 yet still the difference was
  considerable in favour of that leg in 
which the artery remained free4         
,,experiment ,,vi4    ,in two other     
frogs1 in each of which a crural artery 
had been tied1 and  the solution of     
opium 7without regard being paid to     
quantity71  repeatedly injected         

underneath their skulls immediately     
after2 the  contractions appeared to be 
very little weaker in the legs1 whose   
arteries were tied1 than what they were 
in the legs in which they were  not     
tied1 and they continued excitable      
during an equal length of time  in both4
                                        
,,experiment ,,vii4    ,having tied the 
crural artery of another frog1 ,i       
immediately filled  both its stomach and
 abdomen with a strong solution of      
opium4 ,in an  hour after this1 it was  
to appearance quite dead4 ,at the end of
 eight  hours1 the contractions1 excited
 by the metals1 had become very feeble  
in the leg whose artery was tied1 in    
comparison of what they were in  the    
other leg2 and1 at the end of twelve    
hours1 no contractions could  be excited
 in any part of the frog1 except in the 
leg whose artery  remained free4 ,in    
this they continued excitable about an  
hour longer4    ,as it was possible1    
that the more speedy exhaustion of the  

legs1 in  which the arteries were tied1 
might have been owing in some measure to
  the pain1 occasioned by that          
operation1 ,i repeated the experiment   
with  the following variation4          
,,experiment ,,viii4    ,i first divided
 the sciatic nerves1 in both legs of two
 frogs1 and then  tied the crural artery
 in one leg of each4 ,eight drops of the
 solution  of opium were immediately    
afterwards injected upon their brains4  
,but  the event of this experiment was  
precisely the same with the majority  of
 those before related4 ,the contractions
 excited by the metals1 in the  legs    
whose arteries were tied1 were uniformly
 more feeble1 and of  shorter duration1 
than those excited in the other legs3   
yet it is  evident1 that1 in all these  
experiments1 the very reverse of this   
ought  to have taken place1 had it been 
true1 as ,m4 ,fontana has asserted1 that
  opium has no effect upon any part of  
the body1 except through the  medium of 
the blood4    ,the experiments however1 

which ,i am now to relate1 may perhaps  
appear  still more satisfactory4        
,,experiment ,,ix4    ,having laid      
equally bare both the sciatic nerves of 
a frog1 at the  upper part of its       
thighs1 ,i passed a ligature round one  
of them1 and  drew it as tight as it was
 well possible1 without dividing the    
nerve4 ,i  then removed a portion of its
 skull1 and with a small brush1 kept it 
constantly wet with laudanum during     
several hours4 ,the frog soon became    
convulsed2 and1 during ten or twelve    
hours1 continued in that state of       
exquisite sensibility1 which opium never
 fails to produce in these  animals4 ,it
 may here be worth remarking1 that1     
while they are in this  state1 the      
slightest touch of a feather1 or even   
breathing upon them1  excites           
instantaneous convulsions4 ,the leg     
whose nerve was tied1  remained         
paralytic during this time1 but when it 
was laid upon zinc and  excited with    
silver1 it contracted as strongly as the

 other4 ,after  forty three hours1 the  
contractions were very feeble in the leg
 whose  nerve was not tied1 but still   
vigorous in the other4 ,after fifty     
three  hours1 no contractions could be  
excited in any part of the frog1 except 
in the leg whose nerve was tied4 ,in    
this they were sufficiently strong  to  
move the foot1 and continued so for more
 than an hour longer4                   
,,experiment ,x4    ,one of the crural  
nerves of another frog having been tied 
in a similar  manner1 eight drops of the
 strong solution of opium were injected 
upon  its brain4 ,the animal instantly  
became motionless1 but1 in less than an 
hour afterwards1 was considerably       
recovered4    ,the contractions1 excited
 by the metals1 in the leg whose nerve  
was  free1 soon became more feeble than 
those excited in the leg1 whose  nerve  
had been tied4 ,this disproportion1     
between them1 continued  increasing     
during ninety six hours1 after the opium
 had been injected1  when contractions  

could no longer be excited in the leg   
whose nerve  remained free4 ,in that1 in
 which the nerve had been tied1 they    
continued upwards of #d hours           
afterwards4                             
,,experiment ,,xi4    ,immediately after
 having divided the sciatic nerve1 in   
one thigh only1  of three other frogs1  
,i injected as much of the strong       
solution of  opium underneath their     
skulls1 as could possibly be retained4  
,the legs1  in which the nerves had been
 divided1 continued contractile several 
hours after the others had ceased to be 
so4    ,hence1 then1 we see no reason   
for suspecting that the more speedy     
cessation of contractions in those legs1
 in which the crural arteries  were     
tied1 than in those on which no         
operation was performed1 was owing  to  
the pain occasioned by such operation1  
since even the more painful  operations 
of tying or dividing the sciatic nerves1
 were attended with  no such effect4    
,upon the whole1 therefore1 it appears1 

that the conclusion which ,m4  ,fontana 
draws from his numerous experiments with
 opium1 #8,that the  circulation of the 
blood and humours in the animal machine1
 is the  vehicle for opium1 and that1   
without this circulation1 it would have 
no  action on the living body1' is the  
very reverse of that which ,i am        
warranted to draw from the experiments  
,i have just related2 since the  parts1 
most affected by the action of opium1   
were not those in which  the circulation
 remained most entire1 but those in     
which it had been  almost altogether    
interrupted2 and since in two parts     
where the  circulation remained equal1  
and entire1 the action of opium was     
rendered unequal1 by interrupting the   
communication of one of them1 by  means 
of nerves1 with the parts to which the  
opium was applied4    ,the existence1   
consequently1 of any such principle in  
the blood1 as  that supposed by ,m4     
,fontana to exist there1 is rendered far
 too  problematical1 even to allow me to

 expect that it can ever be proved3  far
 less that it may turn out to be the    
same with that discovered by ,m4        
,galvani1 or with that1 whatever it may 
be1 upon which the phenomena of  nerves 
and of muscles may depend4    -----     
,footnote #ac3      ,essays ,physical   
and ,literary4    ,footnote #ad3        
,this solution1 which is the same that  
,i employed in all my subsequent        
experiments1 was of the same strength   
with that used by ,dr ,alexander    in  
the greater number of his1 viz4 an ounce
 of crude opium mixed in a    mortar    
with two ounces and a half of water1 and
 filtered through    paper1 after having
 remained twelve hours1 in a close      
corked bottle1    near a chamber fire4  
----------------------------------------
--------------------------------        
,,appendix4      ,i was unwilling to    
interrupt the narration of the preceding
  experiments1 by the mention of the    
following facts1 which they afforded  me
 an opportunity of observing1 as they   

were not immediately connected  with the
 objects on account of which the        
experiments were instituted2  and ,i    
have yet some few to relate1 which1 from
 the haste with which  these sheets were
 prepared for the press1 ,i had omitted 
to insert in  their proper places4      
#a4 ,in one of my first experiments1 in 
which ,i had occasion to suffer a  frog 
to remain tolerably entire1 so long as  
contractions could be  excited in any   
part of its body1 ,i was surprised to   
find1 on removing  its sternum1 that its
 heart had ceased to contract1 nor could
 be roused  by the application of any   
stimulus whatever1 notwithstanding the  
contractions in its hind legs1 excited  
by the metals1 were still  vigorous1 and
 continued so for several hours         
afterwards4 ,on paying  particular      
attention to this circumstance in       
another frog1 upon whose  brain opium   
had been injected1 ,i found that its    
legs continued  excitable1 upwards of   
forty hours longer than its heart4 ,this

 discovery  of the continuance of the   
contractile power1 in the muscles of the
  posterior extremities1 so long after  
its disappearance in the heart1 is  so  
contradictory to the opinion generally  
received upon this subject1  and long   
established among physiologists1 that ,i
 can scarcely expect it  should be      
credited1 by those who may not          
themselves have opportunities  of       
observing it4 ,it is a fact1 however1 of
 which1 in the course of  these         
experiments1 ,i have had the most       
satisfactory and uniform proofs1  both  
in such frogs as have1 and in such as   
have not1 been under the  influence of  
opium4 ,if a different opinion has      
hitherto been held by  experimentalists 
upon this subject1 it should be         
recollected1 that1  till the discovery  
made by ,galvani1 we had no means of    
ascertaining the  presence of the       
contractile power of muscles1 which had 
not1 at the  same time that they        
indicated its continuance1 a tendency to

 destroy  it1 and consequently to render
 it impossible for us to trace its      
natural progress to extinction4    ,i   
have1 more than once1 observed the same 
circumstance in both cats and  rabbits4 
#b4 ,dr ,alexander1 in his excellent    
,thesis already quoted1 tells us1 that  
the contractility of all the voluntary  
muscles of frogs was destroyed  in the  
course of a very few minutes1 by        
injecting eight drops of a  strong      
solution of opium in water1 7similar to 
that which ,i employed7  upon the       
surfaces of their brains4 ,but that the 
contractions of their  hearts did not   
appear to be much1 if at all1 affected  
by this  treatment4 ,in all the similar 
experiments1 which ,i have made1 the    
event  has been very different4 ,i have 
not found it possible by any quantity1  
either of aqueous or of spirituous      
solution of opium1 injected upon the    
brains of frogs1 to produce that rapid  
extinction of the contractility  of     
their voluntary muscles1 of which ,dr   

,alexander speaks4 ,they commonly       
recovered in less than an hour1 from the
 complete insensibility and  paralysis1 
first occasioned by the injection of the
 opium1 and after  that time1 their     
spontaneous motions almost always       
continued for  several hours longer1    
and1 by the application of the metals1  
contractions were excitable even for    
days4 ,their hearts1 as ,i have  already
 said1 uniformly lost their             
susceptibility of the action of         
stimuli1 long before their posterior    
extremities4    #c4 ,the arguments      
against the antiquated doctrine of      
transudation1  through parts of a living
 body1 are already so numerous and      
satisfactory1 that it may be thought    
unnecessary to notice in this  place1 a 
decisive one so far as relates to the   
skin of frogs1 at least1  which may be  
deduced from the fact already mentioned2
 that so long as  the skin was suffered 
to remain upon the limbs of frogs1      
placing them  in water1 very evidently  

preserved the contractility of their    
muscles1  whereas when the skin was     
taken off1 the muscles became hard1 and 
incapable of contracting1 in a very few 
hours4 ,had there been a  possibility of
 water soaking through the skin1 this   
difference could  not possibly have had 
place4    #d4 ,in speaking of some of   
the relations1 which subsist between the
  influence discovered by ,galvani and  
the nerves1 ,i omitted mentioning  the  
following facts4    ,a very different   
effect is produced by applying the      
metals to the brain  or spinal marrow of
 frogs1 from what is produced by        
applying them to  their nerves4 ,in the 
latter case1 ,i have observed1 that     
every muscle1  to which a nerve below   
the part touched is distributed1 is     
brought into  instant contraction4 ,but 
no muscles are brought into contraction1
 when  the metals are applied to the    
brain or spinal marrow1 except such as  
derive their nerves from the part       
immediately in contact with the  metals4

 ,the influence does not stimulate or   
pass along the spinal  marrow1 as it    
would along the trunk of a nerve1 to    
affect all other  nerves branching off  
from it4    ,i first became acquainted  
with this fact1 while making the        
following  experiment4 ,having laid bare
 the brain of a living frog1 and put a  
stop  to its spontaneous motions1 by    
gently pressing upon the brain1 ,i      
introduced a long slip of tin-foil      
doubled underneath a part of the  skull1
 which had not been removed1 and placed 
a silver probe upon its  tongue4 ,the   
only muscles which contracted1 when the 
tin-foil was bent  over the nose of the 
frog1 so as to come in contact with the 
probe1  were those which move the eyes1 
and the transparent membrane which      
defends them1 those of the tongue and of
 the throat4 ,when the tin-foil  was    
twisted into a thin roll1 and passed a  
little way down the spine1  the muscles 
of the upper extremities and of the     
thorax contracted2 when  a little       

further1 those of the back and of the   
abdomen contracted2 and  when1          
introduced still further1 to where the  
sciatic nerves leave the  spine1 the    
posterior extremities were1 for the     
first time1 strongly  convulsed4 ,i have
 repeated this experiment very          
frequently2 and have  always found1     
that1 as soon as the spontaneous motions
 of frogs had  ceased1 the contractions1
 excited by the metals1 were uniformly  
progressive from the head downwards1    
corresponding exactly to the  progress  
of the metals down the spine4 ,the      
experiment sometimes  succeeds when     
neither the brain nor the spinal marrow 
have been laid  bare1 and when even the 
skin has not been divided1 but1 when the
 frog  is placed upon a plate of zinc1  
and one of the ends of a bent silver    
wire is placed upon any part of its     
spine1 while the other is made to  touch
 the plate4                             
---------------------    #e4 ,as it has 
not been till very lately1 that ,i have 

been able to  procure an electropherus1 
,i have as yet made but few experiments 
with  it2 their result1 however1 is such
 as tends still more to confirm me in   
the opinion1 that the influence1        
discovered by ,galvani1 has no relation 
whatever to electricity4    ,having1    
first1 so far freed the instrument1 from
 the small quantity of  electricity     
collected1 by wiping it1 that none was  
indicated by a very  sensible           
electrometer of linen-yarn1 suspended   
from the wooden part of  its handle2 ,i 
placed it within a few inches of a glass
 stand1 upon  which ,i had laid a plate 
of zinc1 supporting a frog recently     
killed1  and with its sciatic nerves    
within the abdomen laid bare4 ,a bar of 
zinc  formed the communication between  
the frog and the metal plate of the     
electropherus4 ,contractions were then  
excited in the frog1 by placing  one end
 of a bent silver wire1 insulated in    
sealing wax1 upon the  nerves of the    
frog1 and the other end upon the bar of 

zinc4 ,after  strong contractions had1  
in this way1 been kept up for about half
 a  minute1 ,i carefully removed the bar
 of zinc1 by means of a stick of  wax1  
that there might be no possibility of   
the electricity escaping1 if  any should
 have been collected4 ,the metal plate  
was then raised from  the varnished     
surface4 ,the electrometer attached to  
its handle was very  slightly affected2 
but a fine thread1 presented to the     
plate1 was  perceptibly attracted by it4
    ,i had a strong suspicion1 that the 
electricity1 thus collected1 had  been  
excited solely by the friction of the   
frog's legs during  contraction1 against
 the insulated plate of zinc upon which 
it lay2 and  ,i soon found that my      
conjecture was just2 for an equal       
quantity of  electricity was obtained   
from another frog similarly disposed1   
when  contractions were excited in it1  
by merely mechanical irritation4    ,the
 result was the same when these frogs   
were laid successively upon  the metal  

plate of the electropherus itself1 and  
excited1 the one in ,m4  ,galvani's     
method1 the other by mechanical         
irritation only4    ,these experiments  
were very frequently repeated1 but the  
quantity of  electricity collected was  
always greater where the contractions1  
or1 in  other words1 the friction had   
been most considerable1 and did not1 in 
any instance1 appear to depend on the   
means employed to excite the            
contractions4    ,what still further    
proves1 that the electricity1 in this   
way collected1  had no dependence       
whatever1 for its production1 upon the  
application of  the metals to the frog1 
but had been merely the portion of      
electricity1  naturally possessed by the
 frog1 in common with other conducting  
substances1 is1 that when the           
electricity1 which was collected from   
its  first contractions1 had been drawn 
off from the plate1 no more could       
afterwards be collected1 although the   
contractions1 excited by the  metals1   

still continued as vigorous as ever4    
#f4 ,when the electropherus was charged 
with electricity1 as highly as it  was  
possible to charge it by friction1 the  
contractions produced by the  insulated 
metals in a prepared frog1 laid upon the
 metal plate of the  electropherus1 were
 not at all affected by raising it from 
the  varnished surface4 ,a proof that   
the phenomena in question are not       
affected1 either by the condensation or 
rarefaction of the electricity1  in     
either the animal or the metals1 by     
which they are exhibited4    ,i have not
 found1 that any quantity of            
electricity1 which ,i could  accumulate 
in the metal plate of the electropherus1
 did ever1 when  discharged into the    
nerve of a frog1 excite contractions    
nearly so  strong as what are excited by
 the application of zinc and silver2 nor
  could ,i1 at any time1 collect a      
sufficient quantity of electricity1     
from five insulated frogs1 sufficient to
 excite contractions in a  single leg of

 a frog1 though recently separated from 
its body1 and  consequently excitable by
 stimuli of very weak powers4           
---------------------    ,the politeness
 of the very learned ,mr ,robison1      
,professor of ,natural  ,philosophy in  
this ,university1 enables me to lay     
before the public the  following        
communication2 which1 independent of its
 intrinsic merit1  affords an additional
 gratification1 by evincing the great   
interest  taken in the subject1 by one  
whose abilities and extensive knowledge 
so  well qualify him for giving it a    
full investigation4        ,,to ,,mr    
,,fowler1                               
,,edin4 ,may #bh4 #agic4          ,,sir1
      ,about a fortnight ago1 my son    
told me of a curious experiment1 with   
a piece of zinc and a piece of silver   
applied to the tongue1 by    which a    
strong irritation1 resembling taste1 was
 produced1 and that    a luminous flash 
was excited1 by applying one of them to 
the eye4 ,i    immediately repeated them

 according to his directions1 and my    
curiosity was greatly excited to        
prosecute them in a variety of          
circumstances4 ,i understand1 that these
 experiments have originated    from the
 curious discoveries made some time ago 
in ,italy1 of which    ,i was informed  
last winter4 ,but ,i have been so much  
out of the    world for some years past1
 that ,i have had no opportunity of     
knowing what was going forward4         
,being informed1 that you have been long
 engaged in experiments on    this      
subject1 and are about to favour the    
public with an account of    them1 ,i   
have taken the liberty of communicating 
to you1 a few facts    which have       
occurred to me1 some of which1 perhaps1 
may be new to    you4      #a4 ,i find1 
that if a piece of zinc be applied to   
the tongue1 and be    in contact with a 
piece of silver1 which touches any part 
of the    lining of the mouth1 nostrils1
 ear1 urethra1 or anus1 the sensation   
resembling taste is felt on the tongue4 

,if the experiment be    inverted1 by   
applying the silver to the tongue1 the  
irritation    produced by the zinc is   
not sensible1 except in the mouth and   
the    urethra1 and is very slight4 ,i  
find the irritation by the zinc         
strongest when the contact is very      
slight1 and confined to a narrow        
space1 and when the contact of the      
silver is very extensive1 as    when the
 tongue is applied to the cavity of a   
silver spoon4 ,when    the zinc touches 
in an extensive surface1 the irritation 
produced    by a narrow contact of the  
silver is very distinct1 especially on  
the upper side of the tongue1 and along 
its margin4 ,this irritation    seems to
 be mere pungency1 without any          
resemblance to taste1 and it    leaves a
 lasting impression1 like that made by  
caustic alcali4      #b4 ,if the zinc   
7finely polished7 be applied to the ball
 of the eye1    the brightness of the   
flash seems to correspond with the      
surface of    contact1 of the silver    

with the tongue1 palate1 fauces or      
cheek4    ,the same thing happens when  
the silver is applied to the eye4       
#c4 ,when a rod of zinc1 and one of     
silver are applied to the roof of    the
 mouth1 as far back as possible1 the    
irritations produced1 by    bringing    
their outer ends into contact1 are very 
strong1 and that    by the zinc         
resembles taste1 in the same manner as  
when applied to    the tongue4      #d4 
,i had been paring my toe nails with    
scizzars1 and had cut off a             
considerable portion of the thick skin1 
so that the blood began to    ooze      
through1 in the middle of the wound4 ,i 
applied the zinc    there1 and an       
extensive surface of silver to the      
tongue4 ,every time    ,i brought the   
metals into contact1 ,i felt a very     
smart irritation    by the zinc at the  
wound4      #e4 ,i made a piece of zinc 
having a sharp point1 projecting        
laterally from its end4 ,i applied this 
point to a hole in a tooth1    which has

 sometimes ached a little1 and applied  
the silver in an    extensive surface to
 the inside of the cheek4 ,when the     
metals were    brought into contact1 ,i 
felt a very smart and painful twitch in 
the    tooth1 perfectly resembling a    
twitch of the toothack4 ,i thought      
this twitch double1 and that one of them
 happened before the metals    came into
 absolute contact4 ,i am now almost     
convinced1 that this is    the case1 for
 when ,i make the silver rest on a dry  
tooth1 without    touching the tongue or
 fauces1 ,i have no twitch on bringing  
the    outer ends of the metals         
together3 showing that there is not a   
proper communication through a dry      
tooth4 ,if1 while the outer ends        
remain in contact1 ,i touch the silver  
with the tip of the tongue1    still no 
twitch is felt in the tooth4 ,if ,i now 
separate the outer    ends of the       
metals1 keeping the tongue applied to   
the silver1 a    slight twitch is felt  
in the moment of separation1 and a      

strong    double twitch when they are   
again brought into contact4 ,n4 ,b4     
,this    twitch is prevented1 by        
allowing the tongue or lip to touch any 
part of the zinc4      #f4 ,i had a     
number of pieces of zinc made of the    
size of a shilling1    and made them up 
into a rouleau1 with as many shillings4 
,i find    that this alternation1 in    
some circumstances1 increases           
considerably the irritation1 and expect1
 on some such principle1 to    produce a
 still greater increase4 ,if the side of
 the rouleau be    applied to the       
tongue1 so that all the pieces are      
touched by it1    the irritation is very
 strong and disagreeable4 ,this explains
 what    ,i have often observed1 the    
strong taste of soldered seams of metal4
    ,i can now perceive seams in brass  
and copper vessels by the tongue1       
which the eye cannot discover1 and can  
distinguish the base    mixtures which  
abound in gold and silver trinkets4     
,if any of the above facts can add to   

the stock of knowledge you    have      
acquired on this subject1 it will give  
me great satisfaction1    and ,i shall  
not fail to communicate any thing which 
may afterwards    occur4 ,my            
indisposition hinders me from taking an 
active part in    the researches1 to    
which this wonderful and important      
discovery    incites2 but it is both my 
duty and my earnest wish1 to contribute 
my feeble assistance to every gentleman 
engaged in this interesting    pursuit4 
,i find that common silver thread makes 
a very good conductor1 and    this to   
any distance4      ,since writing the   
above1 ,i have found a very easy way of 
producing    very sensible convulsions1 
7,i think muscular7 and corroborating my
    opinion1 that the communication 7of 
this part of the whole effect7    takes 
place before contact4      ,put a plate 
of zinc into one cheek1 and a plate of  
silver1 7a crown    piece7 into the     
other1 at a little distance from each4  
,apply the    cheeks to them as         

extensively as possible4 ,thrust in a   
rod of zinc    between the zinc and the 
cheek1 and a rod of silver between the  
silver and the other cheek4 ,bring their
 outer ends slowly into    contact1 and 
a smart convulsive twitch will be felt  
in the parts of    the gums situated    
between them1 accompanied by bright     
flashes in    the eyes4 ,and these will 
be distinctly perceived before contact1 
and a second time on separating the ends
 of the rods1 or when they    have again
 attained what may be called the        
striking distance4 ,if    the rods be   
alternated1 no effect whatever is       
produced4      ,care must be taken1 not 
to press the pieces hard to the gums2   
this    either hinders us from          
perceiving the convulsion1 or prevents  
it4 ,i    find too1 that one rod1       
whether zinc or silver1 is sufficient   
for    the communication1 and even      
bringing the two pieces together1 will  
do as well1 or perhaps better4 ,but the 
rods are easier in the    management4   

,asking pardon for the liberty ,i have  
taken1 without having the    honour of  
your acquaintance1 ,i am1          ,with
 great regard1                    ,,sir1
                  ,your most obedient   
,humble servant1                        
,,john ,,robison4                       
------------------------------------    
,f ,i ,n ,i ,s4                         
----------------------------------------
--------------------------------        
,transcriber's notes3    ,obvious       
typographical errors were repaired4     
,this included one word  duplicated     
across page boundaries4    ,non-obvious 
8misspellings0 were left alone4         
,possible old spellings inside          
quotations were left alone4