THE BRAIN. 



241 



Gray and White Matter of the Brain. The gray 

 matter of the convolutions of the adult human brain is 

 about one fifth of an inch thick, the larger part of the 

 brain consisting of the white matter. Sections will show 

 that there are several masses of gray matter in the brain 

 deeper than the con- 

 volutions. These ^.AdfeA^ Gray Matter 



are the ganglia of 

 the brain. The 

 white fibers inside 

 the brain connect 

 the gray matter of G an g iia 

 the convolutions 

 and these ganglia 

 with all parts of 

 the body through 

 the spinal cord. 



Cerebrum 



Cerebellum 



Fig. 80. Diagram of -the Brain, showing the Spinal 

 Cord, Ganglia, and Course of the Fibers. 



Neuroglia. The brain consists of nerve cells and nerve 

 fibers, bound together and supported by a form of connec- 

 tive tissue called neuroglia. 



The Cerebrum and its Functions. If the cerebral 

 hemispheres are removed from a frog, he will sit up about 

 as before, but seems to pay little attention to what is going 

 on around him. If placed on his back ; he will turn over 

 and sit up. If pinched, he may jump away, and may show 

 that he can see by avoiding anything that may come in his 

 way. If placed in the water, he will swim, and if he swims 

 against anything that he can climb upon, will do so and 

 remain quiet. If placed on a board, and the board be 

 slowly tilted, he will move along and keep his equilibrium, 

 climbing over the end of the board if necessary to keep his 

 balance. If left alone, he will not move, but will die in 



