344 C. M. JACKSON 



No mitoses were found in one rat (S 33.118), which had been 

 refed six months after maintenance from three to twenty weeks 

 of age. This rat, however, had a body weight of 229 grams, 

 and had nearly ceased to grow. In general, therefore, we may 

 conclude that after one week or more of refeeding the rate of 

 mitosis corresponds in general to that of normal younger rats 

 of similar body weight. 



In these refed rats, however, marked individual variations in 

 the number of mitoses are found, both in different individuals 

 and in different sections of the hypophysis of the same individual. 

 These variations usually have no obvious cause. In one very 

 exceptional case, however, an apparent cause was found. In 

 rat St 1 1 .46 (table 5 C 4) , refed four weeks after maintenance 

 from three to twelve weeks, an astonishing number of mitoses 

 was found in the pars anterior, 107 being counted in one section 

 and 112 in another. This enormous rate of mitosis was appar- 

 ently somewhat evenly distributed throughout the lobe, though 

 no actual counts were made in other sections. It seemed to 

 involve all types of cells. No mitoses were found in the partes 

 intermedia and nervosa. The apparent cause of this abnormal 

 mitosis was found in a small inflammatory lesion near the center 

 of the anterior (distal) lobe, which presented a circumscribed 

 area filled with polymorphonuclear leucocytes. The stimulus 

 from this lesion doubtless caused the proliferation of cells through- 

 out the anterior lobe, while apparently not affecting the remainder 

 of the gland. 



CHANGES IN HISTOLOGICAL STRUCTURE 



The normal histology of the hypophysis in the rat has been 

 described briefly by Tilney ('11, '13) and by Stendell ('14). In 

 the following description, only those features especially con- 

 cerned in the changes during inanition will be considered. 



a. Pars nervosa 



In the newborn rat the pars nervosa in structure resembles a 

 vascular mesenchyme, with numerous stellate or spindle-shaped 



