PLATANISTA. 487 



i.e., on those portions of the horns on which the folds have disappeared and where 

 the wall of the uterus is very thin, the fibres of the mucosa do not exhibit any 

 distinct system of general arrangement over large areas ; indeed, this texture is so 

 fine in many places, especially in the poles of the horns opposed to the Eallopian 

 orifices in both horns, that the surface appears almost smooth. It is not, however, 

 smooth in the true acceptation of the term when used with regard to the mucosa 

 of gravid uteri, because the texture is essentially spongy, as in the uterine mucosa 

 of the mare, tapir, Orcella, &c., but it is so fine that it almost requires a hand-lens 

 to demonstrate its appearance in some places, and it has none of the clear glistening 

 character of the truly smooth spots of the mucosa, wliich are profusely scattered 

 over it. The fibres comprising the mesh work are referable to two distinct groups. 

 The most important group consists of a series of mucous ridgelets having a general 

 course transverse to the long axes of uterine cavities, but on the areas of the 

 primitive folds they become more or less parallel to their direction, and it is on these 

 regions of the horns and uterine cavity that they are most developed, or, in other 

 words, they are the structures which mark the position of the primitive folds of the 

 virgin womb in the left horn, where the latter structures are all but obliterated by 

 the vast extension of that cavity. The divisions and anastomoses of these ridgelets 

 with each other are innumerable, and as they also give off transverse ridgelets they 

 produce a most intricate network of larger and smaller strands, which define irre- 

 gular sunken spaces for the reception of the villi of the chorion. These latter are 

 again divided by minute threads of mucous membrane into little pits, which receive 

 the branches of the chorionic villi. 



On the mucosa of a very advanced uterus no trace of a bare area corresponding 

 to the extensive bare area of the chorion to be hereafter described could be detected, 

 but in another uterus less advanced a narrow branching nude area occurred in the 

 same position as a similar area did in the uterus of Orcella, running up from the 

 waU of the corpus uteri along the septum of the left horn. This bare tract, 

 being irregular in its occurrence and very feebly developed, would appear to be of httle 

 or any physiological significance, but whether when it does exist it may be considered 

 as indicating, of necessity, the existence of a corresponding bare tract in the chorion 

 has yet to be ascertained. 



The OS uteri internum in two gravid uteri is thrown into a series of lamellar 

 folds which overlap each other (PI. XXXI, fig. 2) at their margins, but the area all 

 around the mouth of the womb is finely cryptose with the exception of these 

 points at which the smooth spots occur. The surfaces of the folds are covered with 

 fine mucous ridgelets. 



Around the Fallopian orifices (fig. 3) the uterine surface is cryptose, but the 

 smooth lining membrane of the tube itself is somewhat projected, as it were, into the 

 cavity of the womb as in Orcella, so that a limited bare area occurs within the 

 crescentic fold that defines the orifice. There is no other bare area in this uterus. 



Smooth spots. — The entire inner aspect of the womb from the os uteri to the 

 uterine mouths of the PaUopian tubes is covered over with small circular perfectly 



