PSEUDOPREGNANCY IN THE ALBINO RAT

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Abstract
During the 1st 8 or 10 days of pseudo-pregnancy there was a great reduction in spontaneous activity, an absence of oestrual rhythm, an increase in body wt. and in daily food intake, and a development of the mammary glands similar to that found during the same days of true pregnancy. In 475 cases of pseudopregnancy the av. duration from coitus to the 1st succeeding oestrus was 14.53 days (shortest, was 7 days; longest, 19 days). Pseudopregnancies resulted from positive matings of normal [male][male] with hysterectomized [female][female] and of vasectomized and castrated [male][male] with normal [female][female]. Pseudopregnancy can be induced by artificial stimulation of the cervix uteri. Autopsies made at the 1st oestrus following pseudopregnancy showed typical oestrual conditions of the uteri and ovaries. There was no trace of embryos or of resorption. Pseudopregnancy is not caused by any secretion of the [male] or by young. All the unfertile matings in which erythrocytes were found in the smear following coitus resulted in pseudopregnancy. Many cases, however, in which erythrocytes were not found were observed. Pseudopregnancies were more prevalent in young animals and in those matings made late in oestrus. Evidence indicates that the persistence of the corpora lutea is not caused by a direct nerve impulse to the ovaries. There is a suggestion of a hormone secreted by the mucosa of the vagina, of the uteri, or both, which acts on the corpora lutea either directly or through some intermediary agent, possibly the anterior pituitary gland.

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