212 ANIMAL AUTOMATISM. 



Modern physiology, aided by pathology, easily dem- 

 onstrates that the brain is the seat of all forms of con- 

 sciousness, and fully bears out Descartes' explanation 

 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 stimulants, and of 

 narcotics, it bases the conclusion that thought and 

 emotion are, in like manner, the consequents of physi- 

 cal 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 substance 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 de- 

 pend 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. Lasjtly, 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." 



