BY JAS. P. HILL. ,, 55 



in it, the lateral vaginal canals throughout their entire extent, 

 the urethra and anteriorly the uterine necks and median vaginal 

 cul-de-sacs. In large specimens it may reach a length of as much 

 as 6 cm., and a breadth of 6 mm. Its average length (from the 

 posterior end of the median vaginas to the urogenital sinus) is 

 between 3 and 4 cms., with a breadth of 4-5 mm. 



Fig. 8 represents a transverse section through the mid-region 

 of the urogenital strand of the virgin above referred to. The 

 median ventral portion of the strand is occupied by the urethra 

 (ureth.), while the lateral vaginal canals (l.vay.c.) pass along in it 

 dorso-laterally. The three ducts lie imbedded in the connective 

 tissue of the strand, and strands of the same separate them from 

 each other. Lying peripherally in the connective tissue and 

 surrounding the three ducts is a very thin layer of involuntary 

 muscle. I would direct special attention to the narrow strand of 

 connective tissue separating the lateral vaginal canals, for it is 

 here that the cleft-like pseudo- vaginal passage (3, p- 452) is 

 found to occur after parturition has been effected, but in this 

 strand in the virgin, indeed prior to the tirst parturition, " there 

 is no trace of a median vaginal passage or any epithelial or other 

 track which might indicate the site of a future passage of any 

 kind whatever" (loc. cit. p. 429). The strand in question, as 

 was above mentioned, is directly continuous with the deeper- 

 staining mass of connective tissue situated around and just 

 posterior to the ends of the median vaginal cul-de-sacs. 



The lateral vaginal canals present a uniform structure through- 

 out their course. They are lined by a mucous membrane consist- 

 ing of dense connective tissue, clothed by a layer of columnar 

 epithelium. External to the mucous membrane is a layer of non- 

 striate muscle of no great thickness. The mucosa is thrown 

 into distinct longitudinal ridges. At its posterior end the uro- 

 genital strand Ijecomes continuous with the rounded mass in 

 which the urogenital sinus and cloaca are situated. 



Urogenital Sinus. — The urogenital sinus is a short and narrow 

 chamber with a length of 4-7 mm., having as Owen pointed out 

 (1, p. 683) " the least extent in this genus of Marsupialia." It 



