452 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS. 



The conversion into fibrous texture of the membrane and 

 cells of the stems and branches of the tuft of the chorion, 

 forms the tough white fibrous trunk and branches of the tufts 

 of the foetal portion of the placenta ; in each of which runs a 

 branch of the umbilical arteries and vein ; and the fine mem- 

 brane of the villi of the chorion, with its contained cells and 

 terminal bloodloops, still persistent at the extremities of the 

 villi, are the internal membrane, the internal cells, and the 

 bloodloops described in the first part of this Memoir. 



III. OF THE MATERNAL PORTION OF THE PLACENTA. 



The mucous membrane of the uterus presents on its free 

 surface the orifices of numerous cylindrical follicles arranged 

 parallel to one another, and at right angles to the surface. In 

 the spaces between these follicles the bloodvessels form a 

 dense capillary net-work. 



From the observations of Professors Weber and Sharpey,* 

 it has now been ascertained, that when impregnation has 

 taken place, the mucous membrane of the uterus swells, and 

 becomes lax, that its follicles increase in size, and secrete a 

 granular matter, and that the capillaries increase in a propor- 

 tional degree. " In a uterus," says Dr. Sharpey, " supposed 

 to have been recently impregnated, and in which the vessels 

 had been minutely injected with vermilion, the lining mem- 

 brane, or commencing decidua, appeared everywhere pervaded 

 by a net-work of bloodvessels, in the midst of which the 

 tubular glands were seen, their white epithelium strongly con- 

 trasting with the surrounding redness." It must have been 

 from a uterus in this condition that Von Baer took the sketch 

 of the structure of the commencing decidua, which has been 

 copied by Wagner in his Icones Physiologicce. Von Baer and 

 Wagner, however, have mistaken the enlarged follicles for 



* Miiller's Physiology, page 1574. 



