GROWTH AND STRUCTURE OF HYPOPHYSIS IN RAT 353 



ble that the absence of cell-granules might nuUcate a hyper- 

 functional condition, in which the granules are absorbed too 

 rapidly to allow them to form the normal accumulation in the 

 cytoplasm. Moreover it should be remembered that the granules 

 are rarely absent altogether. In most cases they are found even 

 in extreme inanition, though in scattered areas and more or 

 less reduced in amount. It is likewise evident that the 'colloid' 

 can scarcely be considered as the functional cause of growth, for, 

 although it persists apparently unaffected by inanition, it is 

 normally absent in the very young annuals, in which the growth 

 rate is more rapid. It may indeed be recalled that the most 

 rapid growth of the body in all cases occurs in the early embry- 

 onic period, ]3receding any differentiation whatever in the 

 hypophysis. 



So far as the hypophysis is concerned, therefore, no evidence 

 appears in favor of the suggestion by Osborne and Mendel ('16) 

 that the accelerated growth following periods of suppression 

 may be due to specific histological changes in the ductless glands. 

 Likewise no such changes were found in the thyroid and para- 

 thyroid glands (Jackson '16). Them is. however, some evidence 

 in favor of the view that the rapid growth upon refeeding is 

 due to the embryonic type of structure produced by the inani- 

 tion in the cells of the body in general (Stewart '16). The 

 nuclei become relatively larger and richer in chromatin, the cyto- 

 plasm small in amount and undifferentiated in structure. Ac- 

 cording to the theory of Minot ('07), these are the character- 

 istics upon which the more rapid growth of embryonic cells 

 depend. 



While the cell changes produced by inanition may in general 

 facilitate rapid growth upon refeeding, when pushed to the 

 extreme (as above shown) the cells degenerate to such an extent 

 that recovery appears impossible. This is in agreement with 

 the generally accepted doctrine that severe inanition in young 

 animals may produce permanent stunting of body growth; 

 although Osborne and Mendel ('16) obtained no permanent 

 stunting by long periods of growth suppression in the albino rat. 



THE AMKIUCAX JOrUXAL Of AXATO.MV, VOL. 21, NO. 2 



