Influence of STII and Cortisone on Foetal Growth 171 



shows two characteristics, as shown in Fig. 8. During the 

 first phase of 4-6 days, the retardation in growth compared 

 with the controls is slight, being of the nature of 15 to 20 per 

 cent. From the 6th day the arrest in development is accent- 

 uated and on the 10th day the difference in weight compared 

 with the controls is from 50 to 60 per cent. The majority of 

 the young die between the 12th and the 15th day. Of 50 new- 

 born, 5 reached the age of 30 days and only two have survived 

 two months. Although these two rats partially made up their 

 delay in somatic development during the second month, the 

 genital organs retained their infantile appearance. 



Thus at first sight cortisone proves just as deleterious to the 

 growth of young rats when it is administered during lactation 

 as when it is administered during gestation. 



Conclusions 



The two series of experiments that we have described here 

 show that, in spite of its autonomy, foetal development can 

 be modified by disturbances in the endocrine balance of the 

 mother. 



Contrary to the long accepted opinion, it does not seem 

 feasible that foetal gigantism can be accounted for by the 

 maternal somatotrophic secretion. Although hypophysectomy 

 in the mother on the 12th day of pregnancy does not influence 

 the development of the embryos, the early administration of 

 STH unquestionably inhibits the embryonic development. 

 At the same age, the weight of the foetuses of STH-treated 

 mothers is about half that of the controls, and these embryos 

 are more juvenile in appearance. At 20 days the surfaces of 

 the nervous system and of the visceral organs of these embryos 

 have scarcely reached the stage of development of control 

 embryos of 19 days. If the causes of this growth inhibition 

 still remain unexplained, the fact itself is interesting for it 

 opens up new possibilities of research into the metabolic 

 factors capable of influencing somatic growth. 



The results of cortisone administration show that, in spite 



