HYPOPHYSIS CEREBRI OF CALIFORNIA GROUND-SQUIRREL 193 



/. Pars buccalis 



1 . Pars distalis. The simple classification of the cells of this 

 part into chromophile and chromophobe is not very evident in 

 the ground-squirrel. Transition forms exist in such great num- 

 bers that one kind is not quickly distinguishable from another. 

 There are, however, two extreme types, one deeply granular 

 and the other either slightly so or not at all. 



The deeply chromophile cells are characterized by their larger 

 size and less regular contour. On section they may be round, 

 triangular, square, or polyhedral, in fact, with sufficient search 

 almost any shape may be encountered. The nuclei are round or 

 oval and contain a rich chromatin network. The cytoplasmic 

 granules are coarse and usually irregular in shape. The chro- 

 mophobe cells are characterized by a round, generally smaller, 

 nucleus. The cytoplasm is more or less free from granulation 

 and in many cases consists of only fine protoplasmic strands 

 with no limiting membrane. In this condition they possess no 

 acidophilic properties, the fibers staining a faint tinge with 

 hematoxylin. 



The ground-squirrel hypophysis shows a number of cells vary- 

 ing in granulation from those with none or a few granules to those 

 in which the cytoplasm is practically one homogeneous acidophile 

 mass. The granules of the weakly chromophilic cells are usually 

 small and well separated, the intervening cytoplasm being very 

 weakly acidophilic (fig. 8, a and b). In other cells the granules 

 are larger but fewer in number, presumably due to the coalescence 

 of numerous smaller granules. In the deep acidophiles (fig. 8, 

 c andd) the cytoplasm may show little or no granulation, the cell 

 contents apparently consisting of a mass so densely packed that 

 the ultimate granular nature of it is obscured. 



The distribution of the cells of either extreme of granulation 

 seems to be very irregular, no particular area being recognizable 

 in which either form is more common, for a cell of one extreme 

 may lie adjacent to one of the other (fig. 5, a and b), or be sur- 

 rounded by cells apparently intermediate between the two 

 extremes (fig. 7). Nor does any definite arrangement of the cells 



