Aids to embryology / by J.S. Baxter.

  • Baxter, James Sinclair, 1870-1933
Date:
1948
Catalogue details

Licence: In copyright

Credit: Aids to embryology / by J.S. Baxter. Source: Wellcome Collection.

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    tubules are not fully mature. They are non-motile, and it is not until they have become suspended in the secretions of the accessory genital glands to form the semen that they become functionally active. In this fluid medium they progress in a forward direction by lashing movements of their tails with a speed of from 14 to 23 p, per second. The number of sperma- tozoa per cubic millimetre of semen is estimated to be 60,000, and an average ejaculation contains about 200,000,000. Although it is claimed that spermatozoa may remain alive for a week or longer in the female genital tract, the power to fertilize an ovum lasts only a short time —24 to 48 hours. They are very sensitive to changes in the reaction of the medium, an acid one being very deleterious to them. Abnormalities in the process of spermatogenesis may result in bizarre forms with two or more heads or tails. The Female Organs of Reproduction.—The paired female genital glands are known as the ovaries. The associated genital ducts consist of the uterine tubes, the uterus and the vagina. Of these, the ovary alone will be considered at this time. These glands produce the female germ cells or ova, which, when fertilized by the spermatozoa, develop into new individuals. Like the testis in the male, the ovary is the site of formation of important internal secretions. The ovary is attached at its hilum by a short mesovarium to the posterior surface of the broad ligament of the uterus. Covering the gland, and continuous with the peritoneum of the mesovarium, is a layer of cubical cells termed the germinal epi- thelium since it is the source of ova and their sur- rounding follicle cells. It was formerly believed that ova were only formed during the embryonic period of life, and that these, lying dormant until after puberty,