316 



THE CAT. 



[CHAP. ix. 



made as to a similar objection with respect to the spinal nerves), 

 that we willingly admit the possibility that the excitation of a large 

 fragment of the organ of vision, may produce a fragmentary sensible 

 perception, as also that the grey matter of the interior roots of the 

 organ plays an important part in eliciting the act of sensation, but 

 these admissions do not render it any less rational to suppose that 

 when the whole organic circuit is normal and complete, the animal 

 really sees both in and with its eyes.* 



As to the perception of distance and direction, it may well be that 

 the perceptions of all the special senses besides touch, i.e., colour, 

 sound, taste and smell, can only be localised, not by the nerves of 

 special sense, but by the help of those branches of the fifth nerve 

 a nerve of ordinary sensation which go to those -organs. 



The functions of the nervous system may then be summarized as 

 follows : 



It presides over, stimulates and regulates the alimentary, circu- 

 lating, respiratory, glandular and reproductive processes of the body ; 

 it induces appropriate response to stimuli which are unfelt (reflex 

 action) and to ielt stimuli (sensori-motor action) ; it regulates all 

 the muscular contractions which result in motion, and finally it 

 ministers to all those modifications of "feeling" and all those 

 complex associations and complications of feelings known as imagi- 

 nation, memory, emotion and cognition, to which reference will again 

 be made in the chapter on Psychology. 



* As the different end-organs of the 

 retina perceive different colours, either 

 each such end-organ must be devoted 

 to the perception of one colour only, or 



else each must be capable of stimula- 

 tion by stimuli which are qualitatively 

 different. 



