CHAPTEE IX. 



THE CAT'S NERVOUS SYSTEM AND ORGANS OF SENSE. 



1. WE have now to consider that system of parts which ministers 

 not merely to the processes of organic life, but also to motion, sensa- 

 tion, and cognition. It may therefore be considered as the highest 

 system of parts of which the cat's body is made up. It is so closely 

 connected with motion, and motion is so closely connected with 

 sensation, that these functions would have been here treated of to- 

 gether but for three reasons : The first reason was that the consider- 

 tion of the muscles, as forming so large a part of the body, could not 

 conveniently be postponed ; secondly, the intimate relation of the 

 muscles to the bony levers they move, made it desirable to consider 

 them immediately after the description of the skeleton ; and thirdly, 

 the study of the nervous system can hardly be profitably pursued till 

 acquaintance has been made with all the main organs and parts to 

 which the various nerves are distributed. Such an acquaintance 

 has now been made, and the nervous system remains alone for our 

 ultimate consideration, both as to its structure and as to its functions 

 the most conspicuous of the latter being sensation. All forms of 

 merely physical activity, such as light, heat, chemical change, &c., 

 are indeed separated by a gulf from the activities of organic growth 

 and reproduction, but a gulf hardly less marked divides these latter 

 faculties from one so altogether peculiar and sui generis as is the 

 wonderful power of feeling and cognition. \ 



But although the nervous system is that which MINISTERS TO 

 SENSATION that without which we have no evidence that sensation 

 is even possible nevertheless such a definition of its functions would 

 be very incomplete. The nervous system is the immediate cause of 

 motion, and performs, as we shall see, an intermediate part between 

 the organism containing it, as a whole, and the environing world, 

 since it receives influences from the latter which may excite cor- 

 relative activities in the organism without, as well as with, the 

 accompaniment of sensation. 



It has been before said that an organism is a body in which each 

 part is reciprocally end and means. In animal organisms, this re- 

 ciprocity is generally ministered to and effected by the agency of the 



