272 Frederick Tilney, 



c) Vascularity. The vascularity is particularly rich. 



4. Adult Sheep. Specimen H 41 (plate XI, figs. 13 and 14). 



In its Conformation and general relations the neural portion of the 

 portion of the hypophisis in the sheep closely resembles the animals 

 already described. Its details correspond most nearly to those of the 

 rat. The features which individualize it are the unusual ventral protrusion 

 of the saccular eminence [9\ the relatively short caudal extension of the 

 latter, with a corresponding- increase in the prem animili ary area [6\ 



The angle formed by the junction of the caudal [Olj] and ventro- 

 cephalic [9a\ surfaces is much more acute than is the general rule; 

 in consequence the two surfaces are more nearly parallel to each 

 other. The infundibulum [10] appears as a central extension from 

 the line of junction of these surfaces while its stem is turned directly 

 caudad to become continuous with the infundibular process. The 

 latter process takes the form of a long slender cylinder with a some- 

 what expanded caudal extremity. The recessus tuberis [17] and the 

 recessus infundibuli [8] are both present, but there is no cavity in 

 the infundibular process. The three epithelial portions of the gland 

 are strikingly differentiated in the sheep. The pars tuberalis [12] 

 completely invests the saccular eminence [9]\ the pars infundibularis 

 [13] surrounds the infundibular process and infundibulum, while the 

 pars distalis [14], forming fourfifths of the gland, is separated from 

 the pars infundibularis [13] by a narrow residual lumen [15]. Histo- 

 logically the differences between these three portions are conspicuous. 



1. Histological characters of the pars tuberalis (plate XVIII, fig. 38). 



a) Cellular arrangement. The cells are arranged as a dense cell 

 mass with occasional scattered acini. The acini are small, have thick 

 walls and narrow lumen. 



b) Cells. In the acini the cells are deeply basophilic; the cyto- 

 plasm is scanty, the nuclei oval and picnotic. In the cell masses the 

 cells are faintly basophilic, the nuclei are large and vesicular. 



c) Vascularity. The vascularity is not y&cj rich. 



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

 fìg. 40). 



a) Cellular arrangement. The cellular arrangement is that of 



