2QO APPLIED PHYSIOLOGY 



swelling called the cerebellum, the next two smaller bodies 

 called the optic tubercles, and at the top two larger bodies 

 which together are called the cerebrum. They follow 

 each other in a straight line. In man the parts are bent 

 upon each other, while the cerebrum is so large that it 

 covers all the other parts. 



519. Coverings. The brain of man is a very soft body 

 weighing about fifty ounces. It is contained in the top of 

 fche skull. It is covered with a delicate network of fibers 

 called the pia mater, which carries the numerous blood 

 tubes of the brain. Outside of the pia mater is a 

 thick, tough membrane called the dura mater. The dura 

 mater is the periosteum of the inside of the skull. 



520. The medulla. The upper end of the spinal cord 

 becomes enlarged into a wedge-shaped body called the 

 medulla oblongata, or simply the medulla. The medulla 

 is about one inch and a quarter in length and three quarters 

 inch in breadth at its upper end. Its center is gray matter 

 covered with white matter, both of which are direct con- 

 tinuations of the same matter in the cord. 



521. Nerves of the medulla. From the medulla there 

 go out seven pairs of nerves to supply the head and face. 

 They, together with five other pairs which the brain gives 

 off, are called cranial nerves, in distinction from the spinal 

 nerves. The cranial nerves which arise in the medulla 

 are sensory and motor, and supply the head and face just 

 as the spinal nerves do the rest of the body. They con- 

 nect with cells in the medulla which act only in a reflex 

 way. In this sense, the medulla is a part of the spinal 

 cord, and not of the brain. One of these seven cranial 

 nerves is partly a nerve of the special sense of taste. 

 Impressions of hearing, sight, and smell are carried by 

 three cranial nerves arising higher up in the brain. 



