The diseases of the genital The diseases of the genital organs of domestic animals diseasesofgenita01will Year: 1921 50 Diseases of the Genital Organs occurs immediately following parturition. Ovulation fol- lows about twelve hours later—an interval sufficiently great for the migration of spermatozoa from the vagina to the ovary. In the cow, estrum persists ordinarily for but twelve to twenty-four hours, and ovulation occurs at about the close of this period. If copulation occurs early in estrum, better opportunity is afforded for the arrival of spermatozoa at the pavilion of the oviduct pri
The diseases of the genital The diseases of the genital organs of domestic animals diseasesofgenita01will Year: 1921 50 Diseases of the Genital Organs occurs immediately following parturition. Ovulation fol- lows about twelve hours later—an interval sufficiently great for the migration of spermatozoa from the vagina to the ovary. In the cow, estrum persists ordinarily for but twelve to twenty-four hours, and ovulation occurs at about the close of this period. If copulation occurs early in estrum, better opportunity is afforded for the arrival of spermatozoa at the pavilion of the oviduct prior to the rupture of the ovisac and discharge of the ovum. In swine, carnivora, and to some degree in solipeds, the estrual period is prolonged, extending over several days. In these there are no accurate data of the epoch of ovulation. Probably ovulation occurs at a time corresponding to that observed in the cow—that is, at about the close of estrum. Fig. 25—Diagram of ovary of cow showing comparative sizes of the follicles shown in Figs. 22, 23, 24 The number of ovisacs rupturing at a given estrual period corresponds as a rule with the maximum number of possible fetuses. It is said that rarely two ova are contained in one ovisac. I have been unable to verify this statement, and have in all cases of twins in the cow observed two corpora lutea, sometimes both in one ovary but most frequently one in each. Sometimes a single fertilized ovum divides to con- stitute two embryos, which form identical twins in man, but this is not known to occur in domestic animals, though it probably does so. In multipara, it is assumed that there are at least as many ova discharged, from as many ovisacs, as there are embryos.
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