SEXUAL ORGANS. 53 



what is called extra-uterine or abdominal pregnancy, which some- 

 times occurs in the human subject, can not take place. 



The Uterus exhibits great varieties. It is Simple, uterus simplex, 

 and of a triangular, oval, or round form, according with the human 

 type, while the two oviducts enter its cavity at right angles upon 

 either side of the fundus. This is the case principally in the Apes 

 and Cheiroptera. The uterus is Two-horned, uterus bicornis, in the 

 Ruminantia, Pachydermata, Solipedia, and Cetacea, and in a less 

 degree also in the Makis. The body is here prolonged into a pair 

 of thick and crooked cornua, which pass into the very narrow and 

 much-contorted Fallopian tubes. The uterus is called Divided, ute- 

 rus divisus, where it has only a very short body, as in most Car- 

 nivora, Edentata, and most Rodentia, which speedily divides both ex- 

 ternally and internally, and is continuous with the straight or slightly 

 twisted oviducts. The uterus is actually Double, uterus duplex s. 

 biforis, in some of the Edentata, and in most Rodenlia, as the 

 Mouse and Hare. Each Fallopian tube passes above into an intes- 

 tiniform uterus, which has two completely distinct openings lying 

 near to each other within the vagina. The structure is still more 

 anomalous in the Ornithorynchus ; the oviducts are here not com- 

 pletely separated, but each has inferiorly an expansion, like the ovi-, 

 ducts of Birds, and opens by itself into the cloaca ; between the two 

 apertures lies that of the urinary bladder. 



The uterus of the Marsupiata is very peculiar, and exhibits in the 

 several genera varieties which, however, are not very remarkable, so 

 that its structure in the Kangaroo may serve as an example. The 

 oviducts are at their abdominal extremity surrounded with a folded 

 crown of fimbricfi, and each, very delicate at its commencement, ex- 

 pands into an elongated uterus, in which the small embryos are de- 

 veloped, and attached by a short umbilical cord. Both uteri open 

 into the vagina, which is likewise double, and very peculiarly formed, 

 as it frequently forms a ccecal sac, which is often divided by a sep- 

 tum, into the commencement of which the uteri open. From this 

 arise superiorly the vaginal canals, two handle-shaped and intes- 

 tiniform membranous tubes, frequently contorted, which coalesce in 

 front of the external sexual opening, or kind of cloaca. Through 

 these the small and still imperfectly developed foetus unquestionably 

 reaches the exterior, and is conveyed by a process not yet known 

 into the pouch. 



The Vagina of the Mammalia seldom presents transverse rugae, 

 but usually slight longitudinal folds. At its termination, frequently 



