THE HYPOPHYSIS CEREBRI 461 



consists of a solid mass of cell columns amongst which are 

 numerous blood-vessels. In the cat, according to Herring (7), 

 the cells are of three kinds — small, polygonal cells with little 

 protoplasm, containing few granules, larger cells with fine 

 granules in the protoplasm, and cells which stain very deeply 

 (chromophilic). Herring inclines to the view that these various 

 types merely represent different phases of activity of secretory 

 cells. 



The pars tuberalis in Mammals closely resembles that of 

 birds, forming, as Tilney (22) expresses it, a saucer-shaped 

 structure, perforated for the passage of the pituitary stalk 

 and lying between the pars distalis and the tuber cinereum 



«® 



Fig. 4. 



(P.T.). It consists of lightly staining cells which frequently 

 form acini. 



The development of the hypophysis in Metatheria has 

 been described (Parker, 16), whilst that of Eutheria has been 

 the subject of numerous detailed investigations (Muller(i2) 

 Mihalkovics (13), Salzer (18), Herring (7), Tilney (22), and 

 others). Rathke's pouch arises as an ectodermal invagination. 

 A portion of its dorsal wall remains thin and constitutes the 

 pars infundibularis ; the rest increases in thickness and be- 

 comes converted into the glandular lobe of the adult, either by 

 outgrowth of solid or hollow processes, or by the ingrowth of 

 connective tissue which breaks up the substance of the walls 

 into lobules. The chromophilic and chromophobic types of cells 



