GROWTH AND STRUCTURE OF HYPOPHYSIS IN RAT 



329 



IMales... 

 Females. 



NOSE- 

 ANUS 

 LENGTH 



190 

 179 



BODY 

 WKIC.HT 



grams 



188 

 148 



HYPO- 

 PHYSIS 

 WEIGHT 



0.00685 

 0.00808 



per cent 



82.0 

 86.4 



9.7 



6.7 



PARS 

 NERV. 



pe? cent I per cent 



8.3 

 7.0 



Thus in the females the pars anterior appears to have gained, 

 while the pars intermedia and, to a lesser extent, the pars ner- 

 vosa, have decreased in relative (percentage) weight. 



The question naturally arises as to whether the increased rela- 

 tive size of the anterior lobe in the female is sufficient alone to 

 account for the known sexual difference in the weight of the 

 gland. In the averages above shown, the higher percentage 

 weight in the hypophysis of the female is more than sufficient 

 to account for the sexual difference in the gross weight of the 

 gland upon this basis. But this disregards the fact that in these 

 cases the body weight is higher in the males, which might alter 

 the relations. If, however, we compare female H 70.7 and male 

 H68.il, whose ages and body weights are not very different 

 (see table 1), we still find that the larger hypophysis of the female 

 (0.0099 gram) as compared with that of the male (0.0068 gram) 

 may be accounted for as due chiefly to the heavier anterior lobe 

 in the former (86.2 per cent by volume, as against 80.7 per cent 

 in the male), as shown in table 2. Or, comparing the absolute 

 volumes (not given in the table), in the hypophysis of the male 

 H 68.11 the volumes of the partes anterior, intermedia and ner- 

 vosa were 0.00241 cc, 0.00033 cc. and 0.00025 cc, respectively; 

 while in female H 70.7 the corresponding volumes were 0.00386 

 cc, 0.00034 cc. and 0.00029 cc. Thus the larger hypophysis of 

 the female showed but slight increase in the partes intermedia 

 and nervosa, but a very large increase in the pars anterior. 



It should further be noted, however, that in the rats used the 

 sexual difference in the weight of the hypophysis is not so great 

 as that shown in Donaldson's ('15) tables for rats of correspond- 

 ing weight or body length. To produce this difference would 

 require a greater preponderance of relative size for the anterior 

 lobe of the female than is found in my measurements. It is 



