Influence of STH and Cortisone on Foetal Growth 163 



Method 



We injected the somatotrophic hormone (Choay) in doses 

 of 10 i.u. per day into several groups of pregnant rats. One 

 group was injected daily from the 3rd to 16th day, another 

 from the 4th to 16th and others from the 5th, 6th, 7th and 

 8th to 16th day. In the case of the group treated from the 

 3rd to 16th day we either allowed the pregnancy to con- 

 tinue until term, or removed the embryos on the 20th day 

 of gestation. 



Results 



The administration of STH from the 3rd to 16th day of 

 pregnancy causes a greater increase in the weight of the mother 

 than normal and prolongs the duration of pregnancy by from 

 3 to 6 days. The foetuses, all stillborn, are large, their 

 average weight being 6-7 g. against the 4 • 5 g. of the controls 

 (Fig. 1). 



The removal of the foetuses on the 20th day of pregnancy 

 gave apparently contradictory results. The embryos of the 

 STH-treated mothers are, in fact, smaller than the controls. 

 On the 20th day of pregnancy the average weight of 68 

 foetuses of STH-treated mothers was 1 • 22 g. against the 

 2 • 18 g. of the controls : that is, a difference in weight of 40 per 

 cent compared with the controls (Fig. 2). 



These embryos appear normal, but are much more juvenile 

 in appearance (Mercier-Parot and Tuchmann-Duplessis, 1955). 

 On the 20th day the largest of the embryos of STH-treated 

 mothers resemble control embryos of 19 days and the smallest, 

 control embryos of 18 days (Fig. 3). Microscopic study of 

 these embryos confirms this impression of juvenility. Serial 

 section of several embryos did not, in fact, reveal any anomaly, 

 but a very marked difference in the surface of the various 

 organs is regularly found, both in the central nervous system 

 and in the visceral organs. In fact, the organs of the embryos 

 of mothers treated with STH are comparable in appearance 

 on the 20th day to embryos of 18 to 19 days (Fig. 4). 



The results of these two series of experiments led us to 



