3 io NORMAL HISTOLOGY. 



which color best with basic and only slightly with acid stains, and the larger 

 chromof)hile cells (50-80 ju), so named because of their affinity for certain 

 acid dyes (eosin). The two varieties of cells are intermingled in the anterior 

 lobe ; the eosinophilic cells occupy, in a general way, the periphery and the 

 chief cells the centre of the cords. 



The aggregations of the cells, cord-like or spherical in form and usually 

 without a distinct lumen, lie in close relation to the capillary blood-vessels 

 that ramify between them, supported by the delicate connective tissue frame- 

 work. Here and there, however, the glandular epithelium surrounds a 

 lumen which may contain colloid material, and thus resemble the alveoli of 

 the thyroid body. Such colloid-containing spaces are especially numerous 

 and large in the boundary zone, or pars intermedia, between the anterior 



Chief cells ^ ,.., ^ ,, _ 



Colloid 



Capillary 



Chief cells 



Capillary_ 



FIG. 357. Section of pars intermedia of pituitary body, showing details of structure ; three alveoli con- 

 tain colloid material. X 250. 



and posterior lobes. Even in man, but to a very muqh more marked degree 

 in many of the lower mammals, this zone contains large spaces lined with 

 cuboidal cells and more or less filled with semifluid material. The posterior 

 wall of the interlobar space consists of several layers of cells which varyingly 

 invade the adjoining zone of the posterior lobule. The colloid material is 

 to be regarded, perhaps, as the particular secretion of the glandular segment 

 of the hypophysis, which, moreover, is usually conceded a place among the 

 organs of internal secretion. 



The Posterior Lobe. The posterior and smaller division of the 

 pituitary body is directly attached to the floor of the third ventricle by means 

 of its stalk prolonged from the infundibulum. During the early stages of its 

 development, this lobe is represented by a tubular outgrowth, whose walls 

 partake of the general character of the parent brain-vesicle. In man the 

 lumen within the lower end of the diverticulum later entirely disappears, the 

 posterior lobe being solid. In some lower mammals, notably in the cat, the 

 lumen is retained and, in rare instances, may even communicate with the 

 interlobar space. In the adult condition, the posterior or nervous segment 

 retains few histological features suggesting its cerebral origin. Of the demon- 



