Embryonic Mortality induced Experimentally in the Rabbit

Abstract

SYSTEMIC treatment of the pregnant doe with suitable preparations, for example stilbœstrol, results in the destruction of the entire litter¹. However a surgical approach is required in order to destroy selected embryos. Huggett and Pritchard² induced prenatal mortality in rats by crushing the fœtuses with toothed forceps through the intact uterine wall at laparotomy. Later, Frazer³ employed this technique to produce a standard number of implantations by destroying any in excess of the desired number. In rabbits, Brambell et al. ¹ also used a surgical technique to kill embryos on the 16th or 19–20th days of pregnancy ; in some animals attempts were made to-kill the entire complement of embryos while in others only some of the embryos were treated. The technique consisted of perforating the uterine swellings through the antimesometrial wall of the uterus and stabbing at the embryos with a fine suture needle. Rather surprisingly several of the embryos survived this treatment. During experiments on rabbits⁴ concerning the distribution of embryonic death after implantation, it became necessary to ascertain the effect of the stage of pregnancy when death occurred on the resorption of dead embryos and their placentæ in litters that survived to term. Accordingly, a technique was developed whereby embryos could be killed selectively between the 7th and 17th days of pregnancy. It is the purpose of this communication to describe the application of this technique, which proved to be highly successful.