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



Mare ; the analogous part in the human subject also occasionally presents the same 

 structure, and has even been observed in some cases to extend as a mesial partition 

 inwards towards the uterus. 



In the Marsupiata, where from the small size of the foetus at birth a similar con- 

 formation is permitted to remain as a permanent structure, the vagina is in some 

 genera wholly, and in others partially divided ; but the divided portion in the latter 

 is always that which is nearest the urethro-sexual passage. 



The true uterus is completely divided in all the genera, and each division is of a 

 simple elongated form, as in the Rodentia. 



The superadded complications in the female generative organs of the Marsupiata 

 are not, then, rightly attributable to the uterus, but to the vagina ; and they are of 

 such a nature as to adapt the latter to detain the foetus, after it has been expelled 

 from the uterus, for a longer period than in other Mammalia*. 



These complications vary considerably in the different marsupial genera. On a 

 comparison of the female organs in Didelphys dorsigera, Petaurus pygmoeus, and 

 Petaurus Taguanoides, in Dasyurus viverrinus, in Didelphys virginiana, in Macropus 

 jnajor, and Hypsiprymnus IVhitei, or the Macropus minor of Shaw, I find that the 

 relative capacity which the uteri bear to the vaginae diminishes in the order in which 

 the above-named species follow, and that the external pouch has a progressively in- 

 creasing development, corresponding to that of the vaginse. 



In Didelphys dorsigera the uteri rather exceed the unfolded vaginae in length 

 (PI. VI. fig. 5.). In most Marsupiata the vaginae at first descend, as if to communi- 

 cate directly with the urethro-sexual passage, but in this small Opossum, in which 

 the abdominal pouch consists of two slight longitudinal folds, and the young, as is 

 implied by its trivial name, are transported by the mother on her back, each tube, 

 after embracing the os tincae, is immediately continued upwards and outwards, then 

 bends downwards and inwards, and, after a second turn upwards, descends by the 

 side of the opposite tube to terminate parallel with the extremity of the urethra in 

 the common passage. 



In the Petauri the vaginae, when unfolded, are a little longer than the uteri. On 

 examining a specimen of the Pygmy Petaurist which had two very small young in the 



* It will thus be seen that the mode of considering the marsupial generative apparatus which I have adopted 

 leads to a conclusion, as to its influence on parturition, diametrically opposite to that which Geoffroy St. 

 H1I4AIBE arrives at. He assigns as the cause of the premature birth of the marsupial generative product, the 

 absence of any constriction between the uterus and vagina analogous to the cervix uteri in the ordinary Mam- 

 malia ; but the non-existence of the cervix and os uteri can only be asserted where a portion of vagina is re- 

 garded as uterus. In the comparative sketch of the forms of the uterus given byBuRDACH, (Physiologic, Bd. i. 

 pi. iv.) the vaginal is appended to the uterine apparatus in the marsupial or first form, but omitted in the rest : 

 this does not, therefore, express its true relations. In respect of figure, the uterus of Marsupiata does not de- 

 viate from the perfect or human type in a greater degree than that of Rodentia. Burdach (Ibid. p. 130.) con- 

 siders the vaginse {Seitencanalen) of the Marsupiata as the fully developed analogues of the glandular canals 

 described by Malpighi and Gartner in the female organs of the Ruminants, Pachyderms, &c. ; but these 

 canals lead from the urethro-sexual passage, not to the os tincse, but to the broad ligaments and ovaries. 



