4 ZOOLOGICAL PHILOSOPHY 



faculty peculiar to certain animals, and demanding a special system 

 of organs, while the latter, which does not require any special system, 

 is exclusively the property of all animal organisation. 



So long therefore as these two phenomena continue to be confused 

 as to their origin and results, it will be only too easy to make mistakes 

 in proffering explanations of the causes of the general phenomena 

 of animal organisation. It will be so especially in making experiments 

 for the purpose of investigating the principle of feeling and of move- 

 ment, and finally the seat of that principle in the animals which possess 

 these faculties. 



For instance, if we decapitate certain very young animals, or cut 

 the spinal cord between the occiput and the first vertebra, or push 

 in a probe, there occur various movements excited by the pumping 

 of air into the lungs. These have been taken as proof of the revival 

 of feehng by dint of artificial respiration ; whereas these effects 

 are due partly to the irritabihty not being extinct, for it is known that 

 it continues to exist sometime after the death of the individual, and 

 partly to certain muscular movements which can still be excited 

 by the inhalation of air when the spinal cord has not been altogether 

 destroyed by the introduction of a long probe right down its 

 canal. 



I recognised that the organic act which gives rise to the movement 

 of the parts is altogether independent of that which produces feeling, 

 although in both cases nervous influence is necessary. I notice 

 that I can work several of my muscles without experiencing any 

 sensation, and that I can receive a sensation without any movement 

 resulting from it. But for these observations, I too might have taken 

 the movements occurring in a young decapitated animal, or in one whose 

 brain had been removed, as signs of feehng, and I should have fallen 

 into error. 



I think that if the individual is disabled by its nature or otherwise 

 from giving an account of a sensation which it experiences, and that 

 if it only indicates by cries the pain which it is made to undergo, 

 we have no certain sign for inferring that it receives sensation except 

 from knowing that the system. of organs which gives it the faculty 

 of feeling is not destroyed, but retains its integrity. Muscular move- 

 ments excited from without cannot in themselves prove an act 

 of feeling. 



Having fixed my ideas on these interesting objects, I gave attention 

 to the inner feeling, that is to say, that feehng of existence which is 

 possessed only by animals which enjoy the faculty of feeling. I 

 brought to bear on the problem such known facts as are relevant, in 

 addition to my own observations, and I soon became convinced 



