LECTURE X. 



THE OLDER DOCTRINES OF THE NERVOUS 

 SYSTEM. 



I now wish to turn to the views which have been held 

 in the past concerning the brain and the rest of the nervous 

 system, and concerning the way in which by means of it 

 sensation and movement are carried out. I cannot do better 

 than start with the views which were held by Vesalius. 



Vesalius expounds his views on the nervous system as 

 follows : 



" As therefore the power of the vital soul (that is the sum 

 " total of the vital spirit, or the vital spirit regarded as a whole) 

 "is situated in the substance of the heart, and the power of 

 " the natural soul in the proper substance of the liver, and as the 

 " liver prepares the cruder blood together with the natural spirit, 

 " and the heart the purer blood, which together with the vital 

 " spirit rushes with speed throughout the body, and as these 

 " viscera by means of the canals allotted to them distribute their 

 " products to all parts of the body, so also does the brain in ap- 

 " propriate structures, and in organs properly subserving its work, 

 " manufacture the animal spirit which is by far the brightest 

 " and most delicate, and indeed is a quality rather than an actual 

 " thing. And while on the one hand it employs this spirit for 

 " the operations of the chief soul, on the other hand it is 

 "continually distributing it to the instruments of the senses 

 "and of movement by means of nerves, as it were by cords, 

 " the soul never being lacking in this spirit which may be 

 " regarded as the chief author of the activity of those instruments, 

 " any more certainly than the liver and heart ever leave wholly 



