80 



The Endocrine Organs 



lobe cells which has the appearance of colloid appears to accumulate 

 between the cells. These in some parts come to be arranged round the 

 colloid in the form of vesicles which are not very unlike those of the 

 thyroid gland. Even normally this appearance may be observed in the 

 pars anterior (fig. 52), although it is more characteristically seen in the 

 pars intermedia (figs. 50, c, 53, 54). 



Pars intermedia. As has been stated, the pars intermedia, although 

 well provided with blood-vessels, is far less vascular than the pars anterior. 

 At the circumference of the intraglandular cleft these two parts are con- 

 tinuous into one another without a sharp line of demarcation, although it is 



, i 



- 



^10 



FIG. 51. Portion of pars anterior of ox pituitary. Magnified 300 diameters. A large blood- 

 vessel is seen near the middle of the field. Nearly all the cells are oxyphil. 



possible to distinguish them by the character of their cells. Behind the 

 intraglandular cleft the pars intermedia forms a well-marked layer of 

 varying depth (figs. 49, 52) ; it also extends as a thin stratum over the 

 surf ace, of the pars nervosa, as well as over the neck of the gland which 

 connects the pars nervosa with the infundibulum. The cells of the pars 

 intermedia have not the coarse oxyphil granules which are characteristic 

 of the granular cells of the pars anterior, but they contain fine neutrophil 

 granules staining neither with acid nor with basic dyes. They often 

 surround well-defined vesicles occupied by an oxyphil colloid material : 

 occasionally these vesicles are unusually large and numerous, especially 

 in the neighbourhood of the intraglandular cleft (fig. 52). In addition to 

 these colloid masses, some of the cells of the pars intermedia may often 

 be seen in different stages of conversion into globular hyaline bodies, their 

 protoplasm and nucleus becoming swollen : the latter may have become 

 indistinct or have disappeared. Some of the globules thus produced are 



