Homology of Prooestrous Bleeding in the Dog

Abstract

The prooestrous uterine bleeding of dogs and menstruation of primates have been considered by some physiologists to be very similar and to represent in 2 classes of mammals the result of similar causative factors. (Heape, 1 Marshall. 2 )

We have obtained data from experiments conducted on dogs which we believe strongly indicate that the prooestrous bleeding of the dog is not homologous with the menstruation of primates. The evidence for this belief is as follows: (1) Ovariectomy of 5 dogs in the metoestrous phase did not result in external or profuse microscopical bleeding. In all 5 cases microscopical bleeding occurred as early as the 7th day and as late as the 16th day after ovariectomy. This bleeding was only of one or 2 days' duration. No external or microscopical bleeding was observed after ovariectomy of one immature dog and one dog in oestrus. Ovariectomy of monkeys results in external bleeding of about the same quantity as that seen at the normal menstrual period. (E. Allen 3 ; Morrel et al 4 ; Saiki, in press.) (2) Injection of alkaline extracts of the anterior lobe of the hypophysis 22 which contained the gonad stimulating hormones into 2 dogs with ovaries intact resulted in external bleeding during the period of injection. This bleeding stopped soon after the injections had been discontinued. In monkeys profuse microscopical or external bleeding does not occur during the injection period. A latent period of some days intervenes between the cessation of injection and the appearance of blood. (Hartman 5 ; Saiki, in press.) (3) Control experiments in which castrated dogs were injected with quantities of the anterior lobe extracts sufficient to produce external bleeding in the intact animal did not result in profuse microscopical or external bleeding.