THE PITUITARY 339 



There are three types of mammalian pituitary body. In 

 the first, of which the organ of the cat furnishes an example, 

 the posterior lobe is hollow, and its cavity is in free com- 

 munication with the third ventricle of the brain, and the 

 epithelium of the anterior lobe almost completely surrounds 

 the posterior lobe. In the second type (as, for example, 

 in the dog) the body of the posterior lobe is solid, but the 

 neck is hollow, and communicates with the third ventricle, 

 and the posterior lobe is almost completely surrounded with 

 epithelium, as in the first type. In the third type e.g., 

 man, monkey, ox, pig, and rabbit the body and neck of 

 the posterior lobe are solid, although traces of a cavity are 

 occasionally found in the neck. In this last type the epithe- 

 lium of the anterior lobe does not spread so far round the 

 posterior lobe, but is gathered around the neck and spreads 

 over and into the adjacent surface of the brain (Herring). 

 (Fig. 94.) 



The epithelial portion is again divided into two parts : 

 (1) An anterior lobe proper, consisting of solid columns of 

 cells, between which run wide bloodvessels ; and (2) an inter- 

 mediate portion, which lies between the anterior lobe and 

 the nervous portion, forming a close investment to the latter. 

 (Figs. 94 and 95.) 



The anterior lobe presents all the appearances of a true 

 internally secreting gland. Its structure is clearly that of 

 a gland an "epithelial body," in Kohn's phraseology. It 

 is made up of a branching, compact network of epithelial 

 threads and columns. In the spaces of the epithelial network 

 run wide, thin -walled bloodvessels, so that in many cases 

 the epithelial cells are placed directly on the delicate vessel 

 wall. This arrangement is most admirably adapted for the 

 purposes of internal secretion. The general scheme of structure 

 is the same as in the adrenal cortex, the islets of Langerhans, 

 of the pancreas, the thyroid, and the thymus (in its epithelial 

 stage). (See Fig. 95.) 



The general nature of the cells found in the glandular 

 pituitary may be thus stated : 



((a) Acidophile. 

 . Chromoph,le F 



2. Chromophobe. (See Fig. 95.) 



