IX.] ANIMAL AUTOMATISM. 205 



Modern physiology, aided by pathology, easily 

 demonstrates that the brain is the seat of all forms of 

 consciousness, and fully bears out Descartes' explana- 

 tion of the reference of those sensations in the viscera 

 which accompany intense emotion, to these organs. 

 It proves, directly, that those states of consciousness 

 which we call sensations are the immediate consequent 

 of a change in the brain excited by the sensory nerves; 

 and, on the well-known effects of injuries, of stim- 

 ulants, and of narcotics, it bases the conclusion that 

 thought and emotion are, in like manner, the conse- 

 quents of physical antecedents. 



II. The movements of animals are due to the 

 change of form of muscles, which shorten 

 and become thicker ; and this change of form 

 in a muscle arises from a motion of the sub- 

 stance contained within the nerves which go 

 to the muscle. 



In the " Passions de 1'Ame," Art. vii., Descartes 

 writes : 



" Moreover, we know that all the movements of the limbs 

 depend on the muscles, and that these muscles are opposed to 

 one another in such a manner, that when one of them shortens, 

 it draws along the part of the body to which it is attached, and 

 so gives rise to a simultaneous elongation of the muscle which is 

 opposed to it. Then, if it happens, afterwards, that the latter 

 shortens, it causes the former to elongate, and draws towards 

 itself the part to which it is attached. Lastly, we know that all 

 these movements of the muscles, as all the senses, depend on the 

 nerves, which are like little threads or tubes, which all come from 

 the brain, and, like it, contain a certain very subtle air or wind, 

 termed the animal spirits." 



