174 RIOHAED ASSHETON. 



a piece of uterus is blown out with water, then hardened, and 

 a transverse section cut, the cavity will be seen to be bounded 

 by a semicircular wall on the abmesometrial side, and, by 

 reason of the two largely developed " placental" lobes, a very 

 flattened wall on the mesometrial side. 



Fig. 1, PI. 19, is a figure of the section of the uterus during 

 the early days of pregnancy, or in such part of the uterus in 

 which no embryo is present during rather a later stage in the 

 earlier part of pregnancy. M. is the mesometrium ; C. is the 

 cavity of the uterus. 



The general external outline of the uterus is circular ; so is 

 the inner muscular system, but the latter is eccentrically 

 placed to the outline of the uterus. 



Within these muscular coats, which form the most resisting 

 part of the uterus, comes the soft connective tissue and epi- 

 thelial lining of the uterus. The loose connective-tissue layer 

 seems to be the most yielding, and, as a consequence of the 

 blastodermic vesicle within the cavity of the uterus, the folds 

 or lobes, as they appear in transverse section {PL. L., PP. L.y 

 OP. L), diminish in size, and as the body within increases in 

 size, one by one they begin to disappear. The obplacental 

 lobes have quite disappeared by the middle of the eighth day, 

 and the periplacental lobes can no longer be described as lobes 

 or folds after the beginning of the ninth day. The placental 

 folds being the largest, and also upon the less expansible side 

 of the uterus, become much flattened but never entirely dis- 

 appear. 



About the time that the blastodermic vesicle becomes de- 

 finitely located, its shape is in transverse section as fig. 4. 



The lining of the uterus is seen in fig. 1 to be thrown into 

 folds. When the blastodermic vesicle (fig. 4) is inserted into 

 the cavity, the folds become pressed out to a greater or less 

 extent : thus the folds called obplacental are entirely obliterated 

 [OP. Z/., fig. 2), the periplacental are nearly obliterated, but 

 the placental lobes being very much larger, and also being 

 supported by a larger mass of muscular tissue, are hardly com- 

 pressed at all. 



