680 ANATOMY OF VERTEBRATES. 



The common vestibule, b, is about one inch four lines in length, 

 and varies from half an inch to an inch in diameter : it is lined by 

 a dark- coloured epithelium. The rectum opens freely into it 

 posteriorly, as indicated by the probe b'. On the sternal aspect of 

 the vestibule there are a series of longitudinal fibres, which ex- 

 tend from its external orifice to that of the urogenital cavity, 

 the office of which is to approximate these orifices ; and in this 

 action certain oblique fibres assist, while at the same time they 

 close the rectum. 



On the sternal aspect of the urogenital canal, and close to 

 where it joins the vestibule, the clitoris is situated, which is con- 

 sequently about an inch and a half distant from the external 

 orifice of the vestibule. It is inclosed in a sheath upwards of an 

 inch in length, and about two lines in diameter, of a white fibrous 

 texture, and with a smooth internal surface, and this sheath com- 

 municates with the vestibule about a line from the external 

 aperture. The clitoris itself is a little flattened body shaped like 

 a heart on playing cards ; it is about three lines long, and two 

 lines in diameter at its dilated extremity, where the mesial notch 

 indicates its correspondence of form with the bifurcated penis of 

 the male. 



At the base of the clitoris are two small round flattened glands, 

 the homotypes of Cowper's glands in the mal^, which open into 

 the sheath or preputium clitoridis. 



§ 383. In Marsupialia. — In this order the female organs consist 

 of two ovaries, two oviducts or fallopian tubes, two uteri, two 

 vaginae, an urogenital canal, and a clitoris. 



The ovaries are small and simple in the uniparous Kangaroos, 

 fig. 538, a, a! ; tuberculate and relatively larger in the multi- 

 parous Opossums, presenting the largest size and most compli- 

 cated form in the Wombat, fig. 536. In Macropus they are 

 lodged within the expanded orifice of the oviduct, or ' pavilion,' 

 near the upper or anterior extremities of its two principal 

 lobes. These are of considerable extent, and their internal sur- 

 face, which is highly vascular, is beset with rugse and papilla?. 

 In the Dasyures and Petaurists the ovaries are elliptical, sub- 

 compressed, and smooth. In the Virginian Opossum the ovary 

 consists of a lax stroma remarkable for the number of ovisacs 

 imbedded in it, the largest of which are the most superficial, and 

 give rise to the tubercular projections on the surface. In the 

 Wombat, fig. 536, each ovary, besides being lodged in the pa- 

 vilion, as in the Kangaroo, is inclosed with the pavilion in a 

 peritoneal capsule : it is botryoidal in form, resembling the 



