270 Frederick Tilney, 



pars infundibularis from the pars distalis [14] while the latter is 

 fused with the pars tuberalis [J2]. 



1 . Histological characters of the pars tuberalis (plate XVII, fig. 32). 



a) Cellular arrangement. The cells are arranged in loose cell 

 masses, scattered through which are occasional small, thick-walled 

 acini (generally two cells thick). The acini contain no colloid. 



b) Cells. The cytoplasm of the cells is basophilic and granular. 

 The cells of the acini have less cytoplasm than those in the masses. 

 The nuclei are vesicular in the latter cells and picnotic in those of 

 the acini. 



c) Vascularity. Vascular elements are not numerous. 



2. Histological characters of the pars infundibularis (plate XVII, 

 fig. 34). 



a) Cellular arrangement. The cells appear in a dense mass with 

 a few large, thin-walled acini filled with colloid material. 



b) Cells. The cells in this area are large and basophilic taking 

 the stain somewhat less intensely than the cells of the pars tuberalis. 

 The nuclei are small, oval and picnotic. 



c) Vascularity. Blood vascular elements in this area are very few. 



3. Histological characters of the pars distalis (plate XVII, fig. 33). 



a) Cellular arrangement. The cells here appear in long, con- 

 voluted cords between which ramifies a rich plexus of blood spaces. 

 In addition to the cell cords, cell masses were also observed. 



b) Cells. Tlie majority of the cells are large and acidophilic. 

 Some smaller basophilic cells intermingle with the acidophiles. 



c) Vascularity. The pars distalis is particularly characterized by 

 its rich vascularity. 



4. Adult Rat (Mus Decumanus) Specimen no. H 45 (plate X, 

 figs. 11 and 12). 



The general arrangement of the saccular eminence in the rat 

 differs somewhat from that of the animals already described. It oc- 

 cupies the typical position between the chiasm and the corpora mam- 

 millaria. Its recess forms a large ventral expansion of the third 

 ventricle. Its ventro-cephalic surface is more sinuous than is the 



