348 GENERAL PURPOSES OF NERVOUS SYSTEM. if 
greater complexity of structure, and obviously acquiring 
higher and yet higher functions; so that in Vertebrated 
s, and more especially in Man, it is evidently that 
portion of the organism to whose welfare everything else is 
brought-into subordination (§ 73). And we observe this to be » 
the case, not merely in virtue of its direct instrumentality as 
the organ of Mind, but also in the intimacy of its relation to 
the Organic functions, which are placed in great degree under 
its control. Thus we find that the inlets and outlets to the 
Digestive apparatus, the mechanism by which food is brought 
to the mouth and conveyed into the stomach, and that by 
which indigestible matters are voided from the large in- 
testine, are subjected to its influence ; although the act of 
digestion itself, and the passage of the aliment from one end 
of the canal to the other, are performed independently of it. © 
So, again, the movements of Respiration, by which the air 
within the lungs is renewed as fast as it becomes vitiated, are 
not only effected through its instrumentality, but are placed, 
for the purposes of Vocalization, as far under the control of — ; 
the Will as would be consistent with a due regard to the 
safety of life. Yet among many of the lower tribes of Animals, 
the ingestion of food and the aeration of the circulating fluid - 
“are provided-for by ciliary action alone (§ 45), in which we ; 
have every reason to believe that nervous agency has no pang 7 
ticipation whatever. 
430. If, taking the Nervous System of Man as the highest _ 
type of this apparatus, we analyse in a general’way the actions 
to which it is subservient, we find that they may be arranged 
under several distinct groups, which it is very important to 
consider apart, whether we are studying his psychical + functions - 
or those of the lower animals.—1. The simplest mode of its” 
action is that in which an impression made upon an afferent 
nerve excites, through the ganglionic centre in which it ter- 
minates, an impulse in the motor nerve issuing from it, which, — 
being transmitted by it to the muscular apparatus, calls forth | 
a respondent movement. Of this action, which is called reflem, 
or “excito-motor,” and which may be performed without any 
consciousness Sither of the impression or of the motion, we 
have already seen examples in the movements of Deglutition 
_ 1 This term is used to designate the sensorial and mental endowments 
of Animals, in the most comprehensive sense. 
