MR. OWEN ON THE GENERATION OF THE MARSUPIAL ANIMALS. 351 



and to assume the form of cornua. The mesial cleft increases, and the cornna pre- 

 ponderate in the Carnivora, the Cetacea, the Ruminantia, and the Pachydermata ; but 

 it is in the Rodetitia, which present affinities to Birds in other parts of their struc- 

 ture, that the uterus is first found completely divided into two lateral halves. This 

 structure is not, indeed, uniformly met with in all the genera of the order ; but be- 

 sides the Hare and Rabbit, in which the double uterus is allowed to exist by De Graaf 

 and CuviER*, a similar complete division of the organ obtains in the genera Sc'mrus, 

 Arctomys, Spalax, Bathyergus, Eciiimys, Eretizon (F. Cuv.), and Hydrochceriis ; while 

 in the genera Mus, Cavia, Coelogenys, and Dasyprocta a portion of the true uterus 

 still remains undivided, though this part, to which alone the term corpus uteri can 

 be properly applied, is extremely small or rudimental. Nevertheless, although the 

 corpus uteri exists in these genera, the true vagina is as remarkable for its length 

 and capacity as in those in which the corpus uteri has ceased to exist. 



Hitherto the vagina has presented itself under the form of a simple undivided 

 canal, communicating with the urethro-sexual passage, at least after impregnation, 

 by a single aperture. But it is a remarkable and interesting fact that in the Sloth, 

 in the Mare and Ass, in the Pig, in the Cow, and probably also in other Ruminants, 

 the vagina in the virgin state communicates with the urethro-sexual passage by a 

 double aperture, in consequence of being traversed by a narrow vertical septum or 

 chord. This septum has been described by veterinary authors as a hymen in the 



* The structure of the female generative organs of the Hare and Rabbit was well known to Daubenton, 

 who has given accurate figures of them ; but as he probably regarded the corpus uteri as an essential part of 

 the organ, he describes the true or proper vagina under that name. In speaking, however, of the same paits in 

 the Rabbit, he unconsciously admits the true nature of the latter part, observing, " Chaque come avan9oit dans 

 le vagin de deuxlignes de longeur." — Buffon, Hist. Nat., torn. vi. p. 326. And again observes, that in a rabbit 

 ready to bring forth, " les orifices des comes de la matrice commen^aient a dilater pour 1' accouchement 

 comme I'orifice interne de la matrice se dilate en pareil cas dans la pliipart des autres animaux." 



Supported by the identity of structure in the vagina of the Cavies, in which the true corpus uteri exists, 

 with that of the Hares, and by the authority of Cuvier, I should scarcely have thought it necessary to refer 

 to Daubenton's descriptions had not his views been recently adopted by Geoffroy St. Hilaire and sup- 

 ported by additional arguments, and the same reasoning apphed to the determination of the parts of female 

 apparatus in the Marsupiata. (See Anatomic Philosophique, pi. 17. fig. 13. pp. 397, 398.) According to this 

 author tlie cornua uteri and corpus uteri are distinct elements of the eiferent portion of the genital apparatus, 

 each being composed of a different substance (tissu), nourished from different Eirterial branches, and possessing 

 different functions ; he proposes therefore to name the former aduterum, quasi vas vel marsupium ad uterum. I 

 cannot, however, coincide with this opinion, as I have not been able in any instance to appreciate an essential 

 difference of tissue between the corpus and cornua uteri in those quadrupeds with a partially divided uterus ; 

 and I believe such a difference can only be predicated where, as in the Hare and Rabbit, a portion of the 

 vagina is considered as the body of the uterus ; and that so far from the corpus uteri not participating in the 

 function of gestation, it is always found traversed by the foetal membranes in uniparous quadrupeds with the 

 uterus bicomis, as in the Mare, the Deer, and the Porpesse, in all of which I have dissected the pregnant 

 uterus. And Daubenton expressly records an observation he made on the Mouse, in which the corpus uteri 

 is reduced to the smallest proportional size, that in a pregnant female with five young ones in the uterus, two 

 were in the right corau, two in the left, and one in the corpus uteri. — See Buffon, Hist. Nat., tom. vii. p. 317. 



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