THE NERVOUS SYSTEM 3 



airy in its lightness and transparency, and, 

 like a shadow, it might separate itself some- 

 what from the body. More accustomed to 

 think of an animal as a whole than as an as- 

 semblage of parts, they were prone to conceive 

 of functions as more or less diffusely related 

 to the body. Yet that a certain degree of local- 

 ization was admitted is seen in the opinion 

 ascribed to Galen that the brain is the seat 

 of the rational soul, the heart the location of 

 courage and fear, and the liver that of love. 

 This localization became more or less restricted 

 in later times. Thus, Vesalius taught, in the 

 sixteenth century, that the chief soul was en- 

 gendered in the brain by virtue of the powers 

 of the proper material and form of that organ. 

 And, although Stahl attempted, a century and 

 a half later, to revive the belief that the soul 

 and the sensorium commune were diffused over 

 the whole body, that is, were resident as well 

 in the tip of the finger as in the brain, the idea 

 of the localization of these active properties 

 in the nervous system became so well grounded 

 through the investigations of the physicians of 

 that time, particularly Haller, as to assume the 

 form of permanency. This growth of knowl- 

 edge led directly to the modern view that 



