THE NERVOUS SYSTEM 111 



if they be severed at their union with the cerebellum by 

 a horizontal stroke with a sharp razor. 



Clear away the tissue on the dorsal and lateral side of 

 the cerebral hemisphere, exposing the corpus callosum. 

 Trace it into the hemisphere. Cut through the corpus 

 callosum, expose the cavity of the hemisphere {lateral ven- 

 tricle), and open this ventricle throughout its extent. The 

 anterior horn of the ventricle runs ventrally, bounded 

 medially by the septum pellucidum, and laterally by the 

 convex corpus striatum. The remainder of the cavity fol- 

 lows a curvilinear course, at first posteriorly and laterally, 

 and finally ventrally, terminating near the infundibulum. 

 From the corpus striatum backward the hippocampus 

 forms the median wall of the ventricle. The lateral sur- 

 face of the hippocampus is convex. Viewed from above 

 it forms an angle of about forty-five degrees with the long 

 axis of the brain; from the side it is approximately U- 

 shaped. The lateral and third ventricles communicate 

 through the interventricular foramina {foramina of 

 Munro) . 



Exercise XXIX. Sketch a sagittal section of the brain. 



THE SYIVIP ATRETIC NERVOUS SYSTEM 



The sympathetic nervous system regulates the distri- 

 bution of blood in the body through its control over the 

 nonstriated muscle tissue in the walls of the blood vessels. 

 This regulation is accomplished through variation in the 

 calibre of the vessels, brought about by the contraction 

 and relaxation of these muscles. Sympathetic fibers in- 

 nervate also the respiratory, reproductive, digestive, and 

 other organs, together with their glands. The motor ac- 

 tivities of the system are beyond the control of the will, 

 and the stimulation of its sensory structures does not neces- 

 sarily induce conscious states. 



