HISTOLOGY OF THE HYPOPHYSIS CEREBRI 717 



nucleus. They vary in size, some being smaller than the epithelium cells, 

 others many times larger; they are most numerous in the part of the 

 pars intermedia which merges into the pars nervosa." 



In the sheep's hypophysis (Fig. 7) the interglandular cleft, between 

 the pars anterior propria and the pars intermedia, contains a mass of col- 

 loid which is very definitely stratified, suggestive perhaps, of alternating 

 periods of rest and activity. The desquamated cells in the lumen call to 

 mind like conditions in the thyroid gland. 





Fig. 7. Pars intermedia (p. i.) and pars anterior propria (p. a. p.) of sheep's 

 hypophysis showing lamination of colloid substance (magnification 800). 



Opinions differ concerning the interpretation which we should place 

 upon this colloidal material. Some think that it is a degenerative product, 

 others consider it to be a remnant of a hypothetical external secretion. 

 By far the majority of recent investigators, however, look upon it as a 

 true internal secretion. The increase in amount following thyroidectomy 

 and on removal of the pancreas supports this conclusion. The mode of 

 discharge of the colloid has been much debated. Biedl writes that "the 

 presence of the colloid substance between the cells, in the vesicles, and in 

 the lumen of the capillaries, is regarded as proof of its excretion by way of 

 the blood stream." H3erring has reported the observation of all stages in 

 the passage of the material through the posterior lobe into the cavity of 

 the third ventricle. Atwell and Marnus point out that the material, as 



