318 HITCHCOCK'S ANATOMY 



FlG. 303. 



Yesicular Nerve Corpuscles, a. Cell Wall. I). Cell Contents, c. Pigment, d. Nu« 

 cleus. 6. Prolongation forming Sheath of the fiber. /. Nerve Fiber, magnified 350 diam- 

 eter. 



uring from •? J 77th to ¥7r V <rth of an inch. These are found in 

 the ganglia and the substance of the brain. 



566. Divisions of the Nervous System. — The nervous 

 system consists of a central portion contained within the cav- 

 ity of the skull and the spinal column, and a great number 

 of white threads ramifying through every part of the body. 

 The physical condition upon which the activity of the ner- 

 vous system depends, is the supply of arterial blood. 



567. Cerebrum . — If we examine the parts within the skull, 

 (Fig. 304, p. 319,) we shall find the greater mass of it to be 

 of a spheroidal form, divided nearly into two halves by a deep 

 fissure or cleft, and its surface is singularly roughened by 

 elevations and depressions called anfractuosities. 



568. This mass is the Cerebrum or Great Brain, and the 

 two divisions are called its hemispheres. (Fig. 307, p. 321 ) 



569. In man the average weight of the brain is fifty-four 

 ounces, in females forty-five; the maximum being sixty- four, 



566. What principal divisions does the nervous system consist of? 587. Describe the 

 cerebrum. 569. What is the average weight of the brain? 



