THE DURATION OF ACTION OF CERTAIN NATURAL AND SYNTHETIC OESTROGENS WHEN ADMINISTERED ORALLY OR BY INJECTION

It has been shown by Dodds, Golberg, Lawson, and Robinson [1938] that certain di-esters of diethylstilboestrol have a prolonged action when injected into spayed rats, as have the esters and di-esters of naturally occurring oestrogens. Maximum prolongation of oestrus occurred, however, with the dipropionate, not with the higher esters (dibutyrate and divalerate) of the fatty acid series. This is in contrast to the behaviour of the esters of oestrone and oestradiol, of which the higher esters have a