100 LECTURES ON THE CENTRAL NERVOUS SYSTEM. 



tuber cinereum; thus a funnel-shaped body is formed, the lumen 

 of which is a continuation of the ventricle. At the lower, 

 pointed end of this structure (infundibulum) the hypophysis is 

 attached.* 



The optic tracts pass in a broad curve around the infun- 

 dibulum and over the pedunculi toward the pulvinar of the 

 thalamus. Covered in on both sides by the temporal lobes, they 

 curve upward and outward around the origin of the pedunculi 

 to reach the corpus geniculatum laterale and the pulvinar. 



Farther forward in front of the mfundibulum they are 

 united and form the chiasm from which, after the decussation 

 of their fibres, the optic nerves arise. 



In front of the optic tract, external to the chiasm, just 



under the anterior part of the corpus 

 striatum, lies the substaritia perforata 



JnfanJibu.lu.in. . . , , 



anterior, a grayish mass penetrated 

 by numerous blood-vessels from the 



1 Hypophysis. . . 



pia. In front of it is the region of 





obus t.n/u.natl'Uu 



the lobus olfactorius. 



FIG. 5. The olfactory lobe, in many 



The hypohyisn from behind. animals, is a large organ on the base 



of the fore-brain ; in water mammals 

 it is entirely wanting, while in human beings and apes it is 

 very much atrophied. 



Its anterior, bulbous extremity is called the bulbus olfacto- 



tf 



rius, and its posterior portion, which is continuous with the 

 cortex of the frontal lobe, has received the name of tuber 

 olfactorium. That portion which lies between the two has be- 

 come atrophied to a thin pedicle, the tractus olfactorius. The 



* The hypophysis (Fig. 58). an appendix to the base of the brain, about the size of a 

 cherry, consists, first, of a prolongation of the floor of the ventricle (lobus infundibuli), which is 

 not positively proved to consist of nerve-substance, and, secondly, of a tuft of epithelial tubules 

 which are firmly attached to the lobus infundibuli, and which, as you know, is derived from the 

 mucous membrane of the pharynx. In vertebrates other than mammals this epithelial portion 

 of the hypophysis is not attached to the lobus infundibuli at all. Later researches (Flesch, 

 Darkschewitsch) have shown that it contains two forms of cells, small hyaline and large, 

 granular, nucleated cells. Inasmuch as very similar elements are found in several very active 

 glands, it is probable that the hypophysis has some physiological function to perform. 



