“…Their activity was found to be dependent on the administered dose and the time of pregnancy. They are maximally effective when given immediately after implantation of fertilized ova, that is on day 4 of gestation in the hamster, day 7 in the rat and day 20 in the bitch (Galliani & Lerner, 1976, 1976aGalliani et al, 1977Galliani et al, , 1980Galliani et al, , 1981.…”