78 



The Endocrine Organs 



which are indeed sometimes set closely round the blood-spaces. So 

 abundant are the blood-vessels that a photograph of a section of this part 

 of the injected organ appears almost black (fig. 47) : the contrast with the 

 pars intermedia and pars nervosa being marked. The pars anterior is 

 supplied with blood by about eighteen to twenty small arterioles which 

 converge towards the infundibulum from the circle of Willis and pass into 

 it along the stalk (Dandy and Goetsch). They open into the sinus-like 

 channels which in this part take the place of capillaries ; the blood from 



Fig. 49.— Section of ox pituitary at intraglandular cleft (&), showing on left side (a) a portion 

 of the highly vascular pars anterior, and on right side (c) a portion of pars intermedia. 

 Magnified 200 diameters. 



these passes away by corresponding venules (fig. 48). The pars anterior of 

 the pituitary constitutes one of the most vascular organs in the body. 



The cells of the pars anterior appear as two varieties, viz., clear, non- 

 staining (chromaphobe), and granular, staining (chromaphil) : and the 

 granular cells are again divisible into oxyphil and basiphil, i.e. those 

 staining with acid and basic dyes respectively, the oxyphil cells being 

 normally by far the more numerous. It has been suggested that these 

 three types of cells represent different stages of the same cell; this is 

 probably only true for the chromaphobe cells and for the cells with oxyphil 

 granules. The last-named cells are very distinct (figs. 49 and 50, a, and 

 fig. 51). They may sometimes be seen placed around the blood-sinuses like 



