. Fig. 19. Transverse section across the longitudinal folds at the lower end of the vagina of a 2-1 m. Fin whale foetus, showing two folds and the groove between them. a. Longitudinal muscle layer. b. Epithelium. c. Fibrous corium. d. Apices of the two folds. e. Groove between the folds. /. Developing glands in the groove. An os uteri is present, having the form of a transversely oval prominence. Transverse foldings of the vaginal wall are not found in any Artiodactyle. In the Perissodactyles (rhinoceros) the corpus uteri is short. The cornua are beset by close-set longitudinal folds. The vagi
. Fig. 19. Transverse section across the longitudinal folds at the lower end of the vagina of a 2-1 m. Fin whale foetus, showing two folds and the groove between them. a. Longitudinal muscle layer. b. Epithelium. c. Fibrous corium. d. Apices of the two folds. e. Groove between the folds. /. Developing glands in the groove. An os uteri is present, having the form of a transversely oval prominence. Transverse foldings of the vaginal wall are not found in any Artiodactyle. In the Perissodactyles (rhinoceros) the corpus uteri is short. The cornua are beset by close-set longitudinal folds. The vagina and uterus are not sharply marked off from one another; but the walls of the utero-vaginal canal in this region are thrown into trans- versely circular folds, of which the lowest are the largest. They are alternately arranged so as to give the genital canal a spiral course. The ovaries lie in a peritoneal sac. In the mare the vaginal folds do not exist and the os uteri is marked by a sphincteric thickening of the walls of the canal. It is seen that among these groups of mammals there is little comparison with the Cetacea, since points of resemblance in any group are negatived by equally important differences. The Artiodactyle Ungulates, however, tend to resemble the Cetacea in the implantation of the ovary within the broad ligament in the Ruminants, and the forma- tion of the capsule of the ovary from the fimbriated oviducal funnel in the camel. The folds of the wall of the vagina at the uterine extremity of the passage are seen in Perisso-
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