FEMALE ORGANS OF MONOTREMATA. 679 



in the uterus. The mucous coat is thin and smooth in the ovi- 

 duct ; it is thick, soft, plicated, but not villous, in the uterus. 



The left uterus in a female with a large ovary, shot in the 

 month of September, was two inches long, from four to five lines 

 in diameter, and about a line thick in its parietes ; it became sud- 

 denly contracted and thinner in its coats to form the oviduct, 

 which presented a diameter of about two lines, slightly enlarging 

 to within an inch of the extremity, which forms a wide mem- 

 branous pouch, d" opening into the capsule of the ovary by an 

 oblong orifice or slit, e, of eight lines in extent. The edges of 

 this orifice were entire as in the oviducts of Reptiles, not in- 

 dented as in the fimbriated extremity of the Fallopian tube in 

 higher Mammals. The entire length of the oviduct and uterine 

 tube, when detached from their connections with the mesometry, 

 was nine inches. The right uterus and oviduct of the same 

 specimen exhibited similar differences in diameter and structure, 

 but was shorter, measuring only six inches in length. 



The thickened parietes of the uterine tube depends chiefly 

 on an increase of the inner membrane, which, at the cervix uteri, 

 presents deep and close-set furrows : these, as the canal widens, 

 are gradually lost, and the surface becomes more or less smooth. 

 In the oviduct, the inner surface is smooth on leaving the uterus, 

 then becomes finely reticulate, and in the terminal dilated part 

 becomes again smooth. The cervix uteri makes a valvular pro- 

 jection analogous to an os tincae on each side of the commence- 

 ment of the urogenital canal, just beyond the orifice of the urinary 

 bladder. There are two orifices on each of these prominences : 

 the lower one is the termination of the ureter — a bristle is repre- 

 sented as passing through it in fig. 535 ; the upper or anterior 

 orifice is the os uteri, m. In young or virgin Ornithorhynchi 

 this orifice forms scarcely any projection into the urogenital 

 canal, and it is divided by a narrow septum. The urogenital 

 canal, c, is one inch and a half long, and three or four lines in 

 diameter, but capable of being dilated to as great an extent pro- 

 bably as the pelvis will admit of; the diameter of the bony 

 passage being seven-tenths of an inch. It is invested with a 

 muscular coat, the external fibres of which are longitudinal ; the 

 internal, circular. The inner membrane of this part is disposed in 

 longitudinal rugae more or less marked, but presents as little the 

 character of a secreting membrane as that of the vestibule, being 

 smooth and shining ; the orifices of a few minute follicles are 

 situated in the interstices of the rugae near the orifice of the 

 urinary bladder. 



