880 ANATOMY AND DEVELOPMENT OF MARSUPIALIA, 



layer is practically uniform in thickness(0-08 mm.) except at the 

 two points where the broad ligaments become continuous with 

 it, where it is much thickened. Within the serous layer is 

 the muscular layer composed entirely of plain, circularly 

 running fibres. Blood-vessels pass from this layer into the 

 mucous layer, and penetrate to a point just below the inner 

 epithelium. The mucous layer is characteristically disposed. 

 On the two sides where the broad ligament becomes continuous 

 with the serous layer, the mucosa is much tliickened, forming 

 two large cushion-like projections into the lumen of the uterus, 

 measuring in thickness I'l mm.; on the dorsal and ventral sides 

 of the uterus, however, the mucosa becomes much reduced in 

 thickness, measuringonly 0-19mm. Tlie uterineglands, even at this 

 stage, are somewhat smaller than in the virgin I'erameJes, having 

 a very small lumen, measuring from 001 6 mm. to 0035 mm. in 

 diameter. The mucous membrane is covered by a columnar 

 epithelium measuring, in thickness, about 0*027 mm. 



Uterine Necks. — These(Fig.l, ?t^.M.) resemble externally 

 the Fallopian tubes. Each is quite distinct from the uterine 

 body. Internally the surface of each uterine neck is raised into 

 folds and ridges. Each neck ends in a distinct os, some distance 

 anterior to the point where all the ducts become blended into 

 one mass. The two necks approximate, and run side by side, 

 separated by a w^all of connective tissue 0506 mm. in thickness, 

 wliich, further back, decreases, by further approximation of the 

 necks, to 0-476 mm. Each os is extremely well defined, and of 

 large extent, differing markedly in this respect from the similar 

 structure in Perameles. The os of the left uterus extends through 

 eighty sections of medium thickness. 



Median Yaginal Apparatus . — This consists, on each 

 side, of a median vaginal cul-de-sac, which is quite distinct from 

 its fellow of the opposite side, and separated from it by a thick, 

 complete partition-wall. The right median vagina is considerably 

 larger than the left. The whole ariangement of the median 

 vaginal apparatus is irregular. Each of the median vaginal 

 cul-de-sacs is a large, irregular chamber of no defined shape. The 



