420 STUDIES IN ADVANCED PHYSIOLOGY. 



Immediately behind the optic commissure there is a fun- 

 nel-like projection called the infundibulum. At the end of 

 this infundibulum lies a peculiar gland-shaped body familiar 

 as the pituitary body, a structure described in the chapter 

 on the ductless glands. The infundibulum is hollow, the 

 cavity in the same being an extension of the third ventricle. 

 On account of the thinness of its walls and the difficulty 

 with which the pituitary body is removed from the skull, 

 these structures are usually torn off in prepared brains and 

 the place of the infundibulum is indicated only by an open- 

 ing leading into the third ventricle. 



Posterior to the infundibulum and just in the angle of 

 the crura cerebri lie two small whitish elevations each about 

 the size of a small bullet, the corpora albicantia. It will be 

 pointed out further on that these corpora albicantia are pro- 

 jections caused by the sudden bending back at this point of 

 the fornices, which are bands of nerve fibers running 

 through the brain. These fibers run to the bottom of the 

 brain as if to leave it at this point, and then make a sharp 

 turn and run almost directly backwards. It is this lobe of 

 the fornix which projects from the brain below, and which, 

 consisting of white nerve fibers, gives to these structures 

 their peculiar appearance. 



Following this it may be noticed that the continuation 

 of the cord here divides into two forks, one running to the 

 right hemisphere and the other to the left. These two forks 

 are called the legs of the brain, or the crura cerebri. They 

 are, of course, the big tracts by means of which the hemis- 

 pheres of the brain are put in direct communication with the 

 nervous system below. 



Near the middle of the crura cerebri arises the third pair 

 of cranial nerves, the stumps of which usually appear as rel- 

 atively large nerves. 



A little distance farther back lies the pons Varolii, 

 readily distinguishable as a thickened band around the me- 

 dulla. This pons or bridge consists largely of fibers which 

 run across the cord at this point and connect the two sides 



