168 H. TUCHMANN-DUPLESSIS AND L. MeRCIER-PaROT 



increases protein anabolism, cortisone increases protein 

 catabolism. 



When pregnant rats are treated from the 6th to the 16th 

 day of pregnancy with cortisone in doses of 20 mg. per day, 

 disturbances of gestation and delivery are observed. Courrier 

 and co-workers (1951), like Robson and Sharaf (1952), have 

 similarly observed in the rat and the rabbit disturbances 

 of gestation, abortions and difficulties in delivery under the 

 influence of cortisone and ACTH. 



With the doses of cortisone which we have used (Tuchmann- 

 Duplessis and Mercier-Parot, 1954), abortions in our breeding 

 rats are relatively rare. The foetuses are, in the majority of 

 cases, live, of normal appearance and their average weight is 

 only 10 per cent lower than that of the controls. We have not 

 observed malformations like those reported by Fraser, Fain- 

 stat and Kalter (1953) in mice. 



Nevertheless, in spite of their normal appearance, these new- 

 born rats are extremely frail. Although appearing to nurse 

 normally, that is their milk intake is normal, the majority 

 of the young rats die between the 3rd and 4th day. The 

 growth of the rare survivors is, as shown in Fig. 7, considerably 

 slowed down or completely arrested. Sickly, rapidly becoming 

 senile and wrinkled in appearance, these animals do not 

 generally survive for more than 12 to 18 days. 



Thus, if the administration of cortisone to the pregnant rat 

 only slightly delays embryonic development, it almost com- 

 pletely arrests postnatal growth. 



Two series of experiments were carried out in order to 

 investigate the possible causes of the inhibition of post- 

 natal growth: (1) the exchange of newborn between cortisone- 

 treated mothers and control mothers, and (2) the treatment of 

 control mothers with cortisone after parturition. 



In the first series of experiments out of 10 attempts we have 

 only succeeded so far with one exchange of newborn rats. 

 However, the result seemed noteworthy, for, after an initial 

 delay, the few newborn from the cortisone-treated mother 

 and reared by the control mother, developed relatively well. 



