Age Factor in Some Prenatal Endocrine Events 25 



pound than those which were tried, or at other levels. In any 

 case, the fact that giving ACTH can restore the physiological 

 condition in decapitates allows the supposition that the 

 glycogen storage in the liver is hormonally controlled. 



It then would appear that endocrine factors introduce a 

 turning-point in the carbohydrate metabolism, as they do in 

 the properties of several tissues. In an effort to analyse the 

 significance of this turning-point, it should be established to 

 what extent the glycogen storage system has been changed by 

 the first initial hormonal impulse. Attempts were made to 

 study this point by decapitating after day twenty-five. 



In four foetuses decapitated on day twenty-six and norm- 

 ally grown up to day twenty-nine, the mean value of the 

 liver glycogen was 6-1 mg./g. (range: 3 to 8-7), while in 

 controls the value was about 30 mg./g. ; in eight 26-day-old 

 control foetuses the mean was 5-1 mg./g. (range 2 to 7-35) 

 (Fig. 1). So it appears that decapitating the foetus on day 

 twenty-six stops the rapid increase in glycogen storage norm- 

 ally occurring after this day, but that the liver continues to 

 store new glycogen at about the level to which it was brought 

 before decapitation, since the values are expressed per g. of 

 fresh tissue and since the liver continues to grow. 



Further study is necessary to solve the question under dis- 

 cussion exactly. It should also be determined whether a liver, 

 which has not been stimulated at the right time during foetal 

 life, remains able to respond to delayed stimulation. Such 

 problems involve implications for further postnatal life. 



Conclusions 



The aim of this informal paper was to draw attention to and 

 perhaps to raise discussion on some suggestions resulting 

 from experiments. Although many of the discussed problems 

 are not yet solved, it seems that a pituitary-controlled hor- 

 monal impulse introduces a turning-point in the further pro- 

 perties of some tissues : the case of the sexual structures must 

 be held as conclusive from this point of view. Other tissues, 



