322 ZOOLOGICAL PHILOSOPHY 



phenomenon, not even to the smallest faculty. Hence feeling, which 

 is a faculty, is not a property of any individual part, but the result 

 of an organic function. 



I infer from the above principle that every faculty, that arises 

 exclusively from the functions of some especial organ, is confined to 

 animals which possess that organ. Thus just as no animal can see 

 unless it has eyes, so no animal can feel unless it has a nervous 

 system. 



It is useless to object that light does make impressions on certain 

 living bodies that have no eyes, and affects them in spite of that 

 deficiency : it still remains true that plants and a number of animals, 

 such as polyps and many others, do not see although they move 

 towards the hght ; and that all animals are not endowed with feeling, 

 although they may perform movements when irritated in special 

 ways. 



No sort of sensibiUty (conscious or latent) can, then, be ascribed to 

 animals that have no nervous system, on the mere grounds that they 

 have irritable parts ; I have already shown in Part II., Chapter IV., 

 that feeUng and irritabiUty are very different in character, and are due 

 to quite unlike causes. Indeed the conditions required for the pro- 

 duction of feeling are of altogether another nature from those necessary 

 for the presence of irritability. The former demand a special organ 

 which is always distinct, complex, and extended throughout the 

 animal's body, whereas the latter demand no special organ and give 

 rise only to an isolated and local phenomenon. 



But animals, which possess a sufficiently developed nervous system, 

 possess at the same time their natural irritability and also the faculty 

 of feeling ; they have, without being conscious of it, the intimate 

 feehng of their existence, and though they are still liable to excitations 

 from without, they act by an internal power that we shall shortly 

 examine. 



In some, the activities of this internal power are guided by instinct, 

 that is, by inner emotions produced by their needs and habits ; while 

 in others they are guided by a will that is more or less free. 



Thus the faculty of feeling is exclusively the property of animals 

 which have a sensitive nervous system ; and since it gives rise to the 

 intimate feeling of existence, we shall see that this latter feeling 

 endows animals with the faculty of acting by emotions which cause 

 them internal excitations, and permit them to produce for themselves 

 the movements and actions necessary for the satisfaction of their 

 needs. 



But what is physical sensibihty or the faculty of feeling ? What 

 again is the inner feeling of existence ? What are the causes of these 



