322 ('. M. JACKSON 



son '15 a; '15 b) it was shown that, in youn^- rats held at mainte- 

 nance (constant body weight) by underfeeding, the hypophysis 

 usually increases slightly in gross weight; while in adult rats 

 with acute or chronic inanition the weight of the hypophysis 

 decreases nearly in proportion to that of the whole body. The 

 purpose of the present paper is to present the results of an exten- 

 sion of the investigation, including a volumetric and histologi- 

 cal study of the various parts of the hypophysis. 



This paper forms the fourth of a series of studies upon the 

 effects of inanition on the albino rat, the investigation being 

 supported by a special grant from the research funds of the 

 Graduate School of the University of Minnesota. 



MATERIAL AND METHODS 



The material used included the hypophyses from 91 rats, 

 obtained partly in connection with my previous studies (Jackson 

 '15 a and '15 b) and partly from material collected by Hoskins 

 ('16) and Stewart ('16). The 91 rats included 44 normal (con- 

 trol) rats of both sexes, varying from newborn to about one year 

 of age; 15 rats held at maintenance (constant body weight) by 

 underfeeding beginning at the age of three weeks; 6 older rats 

 subjected to acute inanition and 5 to chronic inanition; and 21 

 young rats refed for various periods after being held at mainte- 

 nance from the age of three weeks to ten weeks or more. 



The diet in all cases was whole wheat (graham) bread soaked 

 in whole milk, the amount being reduced for maintenance and 

 chronic inanition, and cut off entirely in acute inanition. Water 

 was supplied ad libitum in all cases. The loss in body weight 

 during acute and chronic inanition (adults) was about one-third. 



The general data for the rats used are given in table 1. In 

 the first column, the letter indicates the series ('H' = Hoskins; 

 'St.' = Stewart, etc.). The number preceding the decimal point 

 is the litter number; the number following designates the indi- 

 vidual rat. (This does not apply to most of the rats in sub- 

 divisions 'C and 'D' of table 1, however, where the litters were 

 not recorded.) 



