XVI.—Studies on the Reproductive System in the Guinea-Pig: Variations in the Œstrous Cycle in the Virgin Animal, after Parturition, and during Pregnancy

Abstract

In the course of an investigation on the effects of intravitam staining with trypan blue on the uterus and ovaries of the guinea-pig at different periods of the œstrous cycle in virgin animals and after parturition, it was found necessary to have definite information with regard to possible variations in the lengths of the cycles. Stockard and Papanicolaou (1917 and 1919) reviewed the earlier work on the œstrous cycle in this rodent, and introduced the vaginal smear technique by which successive cycles could be studied in the living animal. The results of their researches seemed to indicate that the non-pregnant female guinea-pig comes into “heat” regularly about every sixteen days, and that there are only slight time-variations in the periodic rhythm of a given female, and that among different individuals there is a limited variation in the lengths of the cycles. Practically similar results were obtained by Selle (1922), though Voss (1927) indicated that his cases did not confirm the very regular periodicity.