The structure and development of the reproductive organs of the female African elephant

Abstract

The anatomy of the reproductive tract has been studied in several foetuses and one young calf. The external genitalia are characterized by the position of the vulva immediately behind the umbilicus, and a long urogenital canal extending from the vulva to the vaginal opening, which is within the pelvic girdle. The clitoris is relatively large; its tip is partially enveloped in a fold of skin which is referred to as a preputial fold by some writers, but no true prepuce is formed in either sex. The uterine horns of the foetus traverse a ‘ram’s horn’ flexure such as is found in many ungulates, and the mesometrium is produced into elaborate lappets the significance of which is not known. The blood vessels in the region of the kidneys and ovaries were found to be complex and variable in plan. The abdominal reproductive organs are described. The external musculature of the reproductive tract is described. The retractor clitoris (penis) muscle is of unusual form; the muscles of right and left sides do not meet below the rectum and they do not extend far along the genital canal. The ischio-cavernosus muscle is prominent, as is the levator clitoris muscle which appears to have an important function. These muscles are of comparable size and identical disposition in both sexes, at least in foetal stages. The arrangement is contrasted with that in the horse and with that in the hyena, and the significance of the differences is discussed. The bulbo-cavernosus muscle is similar in disposition in both sexes but it is smaller in the female, where the corpus spongiosum is much less prominent. The urethral muscle (compressor of Cowper’s gland) is absent from the female, where Cowper’s gland is relatively minute. A corpus spongiosum is present in the female and is fairly prominent in the foetus, though not comparable in bulk with that of the male. It does not extend to the tip of the clitoris (or of the penis in the male) but does partially invest this organ near its tip by a lateral extension which is served by an elaborate network of nerves and blood vessels homologous with, and similar to, the blood and nerve supply of the true glans penis typical of many mammals. The corpora cavernosa of the clitoris are invested by a thick tunica albuginea, which also invests the strong median tendon into which the levator muscles insert, and extends part way around the roof of the urogenital canal. The two separate uterine cornua unite to form the body of the uterus but the lumina remain separate for most of its length. Implantation usually occurs in this part of the uterus. The two lumina open simply into a common cavity which in turn opens into the vagina, the os uteri being marked by a relatively massive papilla and a prominent sphincter muscle in the foetus. The obstruction evidently becomes progressively less prominent as development proceeds. The vaginal opening into the urogenital canal is complex in early stages and in some foetuses the opening was not patent. The canals of Gaertner were identified in the foetus and were also found in the calf, where they were relatively minute.