22 Alfred Jost 



on day twenty-eight. It should be noted that the area of the 

 sections almost doubles in the same time, which reduces the 

 number of positive cells per unit of surface area in the oldest 

 group. Such facts, verified on a rather large series of foetuses, 

 strongly suggest that the activity of the pituitary gland passes 

 through a maximum at a stage at which the testes and the 

 thyroid request hypophyseal stimulation. Then the pituitary 

 gland would not progressively increase its physiological work 

 in parallel with the progress of its gross anatomical differen- 

 tiation, but would release a larger amount of hormone during 

 a limited period of time. 



The incidence of the age factor on the relationship between 

 hypophysis and adrenal cortex was studied with Miss A. 

 Cohen on a small series of foetuses and some preliminary 

 indications were obtained which require verification. 



The rabbit adrenal cortex provides a less favourable 

 material than that of the rat, its structure being less clearly 

 denned and more variable. On day twenty-eight the cortex 

 shows an external zone organized in large arcads and rather 

 irregular internal cords, which centrally more or less penetrate 

 into the medulla; other cortical cells are mixed with the medul- 

 lary cells. In foetuses decapitated before day twenty-one or 

 twenty-two and studied on day twenty-seven or twenty- 

 eight the zone of arcads is relatively larger and the internal 

 part markedly reduced. The ratio, width of the arcad zone to 

 width of the internal part, is definitely in favour of the arcads, 

 while in controls the internal part largely exceeds the zone 

 of arcads. On the contrary, in foetuses decapitated on day 

 twenty-six and studied on day twenty-nine, the internal part 

 remained large. These preliminary observations seem to 

 indicate that decapitating the foetus before the cortex is 

 organized terminates in a more marked reduction than 

 decapitating at later stages. 



In the rat foetus the adrenal cortex grows markedly from 

 day sixteen to day twenty-one; at about the age of nineteen 

 days, modifications in the lipid content of the cortex suggest 

 changes — probably an increase — in the physiological activity 



