THE FUNCTION OF (ESTRIN 133 



it would produce 500 times as much as the ovaries; yet 

 no symptoms of oestrus occur during pregnancy, and the in- 

 jection of oestrin during pregnancy leads to abortion. If, 

 on the other hand, the presence of oestrin in the placenta in 

 such large amounts is not due to its elaboration there, it is 

 necessary to have some working hypothesis as to the reason for 

 its occurrence. It has been suggested (506) that the placenta 

 absorbs oestrin from the maternal circulation in order to protect 

 the male foetuses from its action. As Lillie (363) has pointed 

 out, the male foetus must be protected in some manner from the 

 sex hormones of the mother, and in view of the reported 'anti- 

 masculine' action of oestrin it is not improbable that some such 

 mechanism does exist. 



