THE PITUITARY BODY 977 



F. THE PITUITARY BODY OR HYPOPHYSIS CEREBRI 



Position and Structure of the H3rpophysis. — In human beings this 

 stru(3ture Hes at the base of the brain directly behind the optic chiasma; 

 and occupies a niche in the sella turcica of the sphenoid bone. It 

 appears as a reddish-gray mass of about the size of a pea which is 

 connected with the ventricular region of the brain by a narrow stalk, 

 called the infundibulum. The body of this gland consists of two lobes, 

 aii anterior and a posterior. They are closely approximated, the cleft- 

 hke space between them being filled with a yellowish fluid. Owing to 

 the fact that the cells lining this space posteriorly, present several 

 distinctive structural features and doubtlessly secrete the aforesaid 

 fluid, they are commonly regarded as forming a special part of the 

 pituitary which is known as the pars intermedia. Gross anatomically, 

 however, these cells belong to the posterior lobe. 



The two lobes of the hypophysis differ widely from one another in 

 their structure, development and function. The posterior one is 

 developed as a hollow outgrowth of that part of the embryonic brain 

 which later on becomes the third ventricle. While this communica- 

 tion is obliterated in man, it remains open in certain animals. The 

 anterior lobe first appears as an extension of the ectoderm of the buccal 

 cavity. After the obliteration of this prolongation, the epithelium 

 arranges itself in the form of trabeculse which are invested by a close 

 network of uncommonly large capillaries, and contain certain cells 

 which are sharply differentiated from the others by their content in 

 deeply staining granules of chromophil. Contrary to the general 

 neuroglia-like character of the posterior lobe, the pars intermedia has 

 the appearance of ependymal tissue. Herring^ has called attention 

 to the fact that these cells embrace a material which stains in the form 

 of globular masses of colloid-like material. From this brief structural 

 survey it may be gathered that the anterior lobe possesses the character- 

 istics of a ductless gland which discharges its product directly into the 

 blood-stream, 2 while the intermediate part discharges its secretion into 

 the infundibular space and the cerebral ventricles. The structure of 

 the posterior part, on the other hand, would not lead us to infer that 

 it possesses a secretory function. 



Removal of the Hypophysis. — The experiments of Horsley (1885), 

 Dastre (1889), and Clay (1891) have shown that the total removal of 

 the hypophysis is followed by death within a few days, the symptoms 

 displayed by these animals being similar to those following the extir- 

 pation of the thyroid or adrenal bodies. Bui since this organ is very 

 inaccessible, some of these symptoms may not be caused by the loss 

 of the hypophysis at all, but by injuries to neighboring parts, such as 

 the tuber cinereum with which its anterior portion lies in close contact. 

 This possibility, however, does not seem to have played an actual 



1 Quart. Jour, of Exp. Physiol., i, 1908, 121. 



2 Bell, ibid., xi, 1917, 77. 



62 



