FEMALE GENITAL SYSTEM: INTERNAL ORGANS 



409 



Comparing the condition of the uterus and vagina of the Cetacea with that of other 

 mammals, we find the uterus bicornis also in Insectivora, Carnivora (Fissipedia and 

 Pinnipedia) and Ungulata (Perissodactyla and Artiodactyla). 



In the Insectivora there is either no os uteri marking 

 off a distinct corpus from the vagina (the mole and the 

 shrew) or, as in the hedgehog, there is an os uteri and 

 a short corpus. The vagina has transverse folds at its 

 uterine extremity. The ovaries are always enclosed in 

 a peritoneal capsule. There is a marked plica diaphrag- 

 matica. 



In the Carnivora (Fissipedia) the os uteri is well 

 developed and the corpus uteri short and wide. The 

 vagina usually lacks the marked transverse reduplications 

 of its walls seen in the Cetacea and some Insectivores. 

 The ovaries are enclosed in a capsule formed by the 

 peritoneum. In the Pinnipedia the corpus is also short 

 and the cornua, as in the Cetacea, continue separately 

 for some distance after they appear externally joined. 

 The ovaries are enclosed in peritoneal capsules. 



Among the Artiodactyle Ungulates the camel shows 

 a short corpus. There is no definite os, but the uterus 

 is marked off from the vagina by a series of nearly trans- 

 verse folds which almost but not quite complete the 

 circle. The capsule of the ovary seems to be formed by 

 the fimbriated oviducal funnel. In the deer, antelope, 

 ox and sheep the ovary is lodged in a recess or sacculus 

 of the broad ligament, such as many authors describe 

 for various Cetacea 



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- 



