THE BRAIN. 591 
others still. It is not to be forgotten that in the brain, as in the 
spinal cord, nerve-cells are themselves conductors, and while 
there may be certain areas within which the resistance is such 
that impulses are usually confined to them, it is also true that, 
as in the cord, there may be a kind of overflow. Adjacent cells, 
possibly widely separated cells, may become involved. We shall 
return to this important subject again, however, as, without 
recognizing such relationships, it seems to us quite impossible 
to understand the facts as we find them in the working of the 
body and the mind. 
The Cerebral Cortex We may now proceed to inquire what 
are the functions of the cells of the gray matter covering the 
surface of the cerebrum. Before the birth of physiology as a 
science, Gall recognized and taught that the encephalon is a col--: 
10 
00 
agoy ponth 
Middle Occip, Con, 
suog 7042039) 
Fig. 881.—Diagrammatic representation of external surface of left cerebral hemisphere of 
man (after Flint and Ecker). 
lection of organs; that these have separate functions; that the 
relative size of each determines the degree of its functional ac- 
tivity; and that the cranium developing in proportion to the 
growth of the brain, the former might give information as to 
the probable size of what lay beneath it in different regions. 
