IX.] ANIMAL AUTOMATISM. 203 



fundamental conceptions to those of Descartes ; and I 

 shall now endeavour to show that a series of proposi- 

 tions, which constitute the foundation and essence of 

 the modern physiology of the nervous system, are 

 fully expressed and illustrated in the works of 

 Descartes. 



I. The brain is the organ of sensation, thought, 

 and emotion ; that is to say, some change in 

 the condition of the matter of this organ is the 

 invariable antecedent of the state of conscious- 

 ness to which each of these terms is applied. 



In the " Principes de la Philosophie" ( 169), 

 Descartes says : * 



" Although the soul is united to the whole body, its principal 

 functions are, nevertheless, performed in the brain; it is here 

 that it not only understands and imagines, but also feels ; and 

 this is effected by the intermediation of the nerves, which extend 

 in the form of delicate threads from the brain to all parts of the 

 body, to which they are attached in such a manner, that we can 

 hardly touch any part of the body without setting the extremity 

 of some nerve in motion. This motion passes along the nerve to 

 that part of the brain which is the common sensorium, as I have 

 sufficiently explained in my Treatise on Dioptrics; and the 

 movements which thus travel along the nerves, as far as that 

 part of the brain with which the soul is closely joined and united, 

 cause it, by reason of their diverse characters, to have different 

 thoughts. And it is these different thoughts of the soul, which 

 arise immediately from the movements that are excited by the 

 nerves in the brain, which we properly term our feelings, or the 

 perceptions of our senses." 



1 I quote, here and always, Cousin's edition of the works of 

 Descartes, as most convenient for reference. It is entitled " (Euvres 

 completes de Descartes," publiees par Victor Cousin. 1824. 



