304 THE CAT. [chap. ix. 



them tlirougli a foramen — the internal auditory meatus and the 

 optic foramen. Both contain two internal fluids enveloped by proper 

 membranes — the perilymph and the aqueous humour, and the 

 endolymph and the vitreous humour. Both have a muscular 

 apparatus to regulate the organ according to the quantity of special 

 influence brought to bear upon it — the muscles of the ossicles and 

 of the iris. Both have the action of the special influence intensified 

 by contained hard parts — the otoconia and the lens — and, finally, 

 both have their nerve of special sense expanded and ending in 

 minute filaments on the innermost membrane of their respective 

 structures. 



§ 28. The FUNCTIONS of the nervous system of the cat are 

 activities the existence and nature of which can be ascertained only : 

 (1) by more or less complex inferences deduced from what human 

 beings can by self- consciousness learn as to their own affections, 

 feelings and cognitions ; (2) by conversation ; (3) by the observa- 

 tions of pathology ; and finally (4) by what can be ascertained as to 

 other creatures by means of experiments upon different animals. 



Such inferences and observations show us that not only muscular 

 motion and sensation depend upon nervous influence, but that even 

 such functions as respiration, digestion, secretion, and excretion, 

 are similarly modified, and that the circulation through the body of 

 the nutritive fluid is greatly acted on — acclerated or retarded — by 

 the same influence. 



For the perfect performance of all the nervous functions the 

 integrity of the whole nervous system is a generally necessary 

 condition. Nevertheless, partial mutilations of different regions 

 of that system produce very different results, proving that all parts 

 have by no means the same activity, but that rUf/'crcnt 2)arts have 

 different fundiom, and that some parts are much more necessary 

 than are others to the maintenance of healthy life. When the 

 destruction of any part of the nervous system induces the cessation 

 of some function, the fact of that 'cessation does not indeed prove 

 that such part is the very organ of such function, but it certainly 

 shows that the non-destruction of such part is a sine qua non for its 

 performance. 



Although we find that the powers of sensation and motion are so 

 mixed up in ourselves that, when the body is entire, the existence 

 of the latter involves the occurrence of the former, while any inten- 

 sity of the former (sensation) produces almost inevitably some amount 

 of the latter (motion) ; nevertheless observation and experiment 

 prove that in abnormal conditions, either can occur without the 

 other ; and the parts which minister to sensation alone or only to 

 motion, are severally named sensohy or motor parts of the nervous 

 system. 



Our consciousness makes plain to us that we not only feel, but 

 that we have very diflTorent kinds of feelings. Apart from ordinary 

 common sensation, apart from feeling as to temperature and from 

 visceral feelings, and feelings due to muscular action and the 



