Chap. II.] 



A NERVOUS SYSTEM. 



53 



In higher ver- 

 tehrates, such as 

 Birds and Mam- 

 mals, we have this 

 same fusion of gan- 

 glia in the spinal 

 cord (fig. 19), whilst 

 a similar process 

 also displays it- 

 self to a more 

 marked extent in 

 the brain. In the 

 higher forms of 

 this series, and 

 above all in Man 

 himself, the gan- 

 glia of the brain 

 become more and 

 more integrated, 

 and some of these 

 parts also take 

 on an enormous 

 development. 



The weight of 

 the entire Brain, 

 as compared with 

 that of the Spinal 



Cord indeed Un- ^^^' 20.— General view of Nervous System of Man, from 

 ' ' . behind. 1, Cerebi'um ; 2, cerebellum ; 3, upper part of 



dergoes a great in- spiuaicord. (Mivart.) 

 crease in each divi- 

 sion of the vertebrates. In the Lamprey this relation is 

 said* to be as 'OlS to 1 ; in the Newt as '55 to 1; in the 

 Pigeon as 3*5 to 1 ; in the Mouse as 4 to 1 ; whilst in 

 * Marshall's " Outlines of Physiology," vol. i. p. 406. 



