DESCARTES'S DOCTRINE. 609 



the auditory, olfactive, and other nerves that pass to them, The ce halLc 

 and preserve the vestiges thereof; for, if this be not the case, ganglia are 

 it is wholly impossible to explain how insects should have the W8 ^ ef8f 

 power of remembering, even though it be indistinctly or imperfectly, 

 things that are past : those things or effects must have left upon them 

 an enduring mark. 



The ganglia of the ventral cord, with their related nerve trunks, con- 

 stitute a series of automatic nerve arcs, their immediate ob- ... - .. 



' f Action oi the 



ject being locomotion. As has been said, the impression of ventral cord 

 the surface upon which the insect rests gives rise, under or- a 

 dinary circumstances, to muscular contraction, and thereby motion, and 

 the same thing occurs under circumstances of unusual experimental dis- 

 turbance, as when irritation of any kind for instance, the pungent va- 

 por of ammonia is applied to one side of a centipede, the body is flex- 

 ed in such a way as to get rid, as far as possible, of the noxious fume. 

 These movements are purely reflex, and in their production the cephalic 

 ganglia are in no manner concerned. 



Guiding and controlling these purely reflex operations, the cephalic 

 ganglia, by means of the fibres which they send in -company Controlling 

 with the trunks of the ventral cord, can exert their influence actl n of the 



cephalic gan- 



in the remotest part of the body. That influence we distin- glia. 

 guish as being of a twofold nature : in part it is due to impressions 

 which are being at that moment received through the various organs of 

 sense the eye, the ear, or whatever other such organ the insect under 

 consideration may possess, and in part arising from the residues of old 

 impressions which the ganglion has formerly received. It does not 

 therefore seem possible, at least as regards the more perfect of these 

 tribes, to accept the views of Descartes, who regarded all insects as mere 

 automata. They are automata only so far as the action of Descartes's 

 their ventral cord and that portion of their cephalic ganglia ^jg Vrctu- 

 which deals with contemporaneous impressions is concerned, tomata. 

 but they are not automata, since they are under the influence of those 

 ganglia as the registers of past impressions. 



What has been said respecting insects applies to all higher tribes of 

 life. Man himself is no exception. In the preceding book we have shown 

 that, so far as his spinal nervous system is concerned, he is simply an 

 automaton, and that it is the development of a brain thereupon which 

 makes him capable of voluntary action. We have seen that in his indi- 

 vidual progress part is evolved from part, an ever-increasing complexity 

 and an ever-continuing improvement. Cerebral mech 



It is the same, also, with the group to which he belongs anism in ani- 

 the vertebrates. Just in proportion to the advance of their 

 cerebral mechanism are their psychical powers. The amphi- powers. 



QQ 



