THE STRUCTURE OF THE HUMAN PLACENTA. 57 



face 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 blood-vessels form a dense capillary 

 network. 



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 mat- 

 ter, and that the capillaries increase in a proportional degree. 

 " In a uterus," says Dr. Sharpey, " supposed to have been re- 

 cently impregnated, and in which the vessels had been minutely 

 injected with vermilion, the lining membrane, or commencing 

 decidua, appeared everywhere pervaded by a network of blood- 

 vessels, in the midst of which the tubular glands were seen,, their 

 white epithelium strongly contrasting with the surrounding red- 

 ness." It must have been from a uterus in this condition that 

 Baer took the sketch of the structure of the commencing deci- 

 dua, which has been copied by Wagner in his Icones Physio- 

 logicce. Baer and Wagner, however, have mistaken the enlarged 

 follicles for papillae, and have represented the capillary loops in a 

 manner much too formal. I have examined a uterus which was 

 in a state described by Dr. Sharpey. There was a well formed 

 corpus luteum in one of the ovaries ; the decidua had appeared on 

 its internal surface, and presented in the most distinct and 

 beautiful manner the orifices of the follicles, and the vascularity 

 of the inter-follicular spaces. The follicles, bounded by their 

 germinal membrane, were turgid with their epithelial contents. 

 The inter-follicular spaces in which the capillaries formed a net- 

 work with polygonal or rounded meshes, was occupied by a tex- 

 ture which consisted entirely of nucleated particles. This is the 

 tissue represented by Baer and Wagner, described by them as 

 surrounding what they supposed to be uterine papillae, and con- 

 sidered by them as decidua. The free surface of the uterine 

 mucous membrane was covered by a membrane, which ap- 

 peared to me to be continuous with the germinal membrane of the 

 follicles. 



* Miiller's Physiology, page 1574. 



