STRUCTURE OF HUMAN PLACENTA. 453 



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 vascu- 

 larity of the interfollicular spaces. The follicles, bounded by 

 their germinal membrane, were turgid with their epithelial 

 contents. The interfollicular spaces in which the capillaries 

 formed a net-work with polygonal or rounded meshes, was 

 occupied by a texture which consisted entirely of nucleated 

 particles. This is the tissue represented by Von Baer and 

 Wagner, described by them as surrounding what they supposed 

 to be uterine papillae, and considered by them as decidua. The 

 free surface of the uterine mucous membrane was covered by 

 a membrane which appeared to me to be continuous with the 

 germinal membrane of the follicles. 



Dr. Sharpey has not described this interfollicular sub- 

 s.tance, as his attention appears to have been chiefly directed 

 to the follicles. As, however, it is to this interfollicular sub- 

 stance, as much as to the enlargement of the follicles them- 

 selves, that the mucous membrane owes its increased thickness, 

 it appears to me worthy of being recorded. 



A uterus in the condition which has just been described, 

 is said to be lined with the decidua, consisting, as has been 

 stated, of an interfollicular cellular substance, and of an ex- 

 tended net-work of capillary bloodvessels. 



About the time at which the ovum reaches the uterus, the 

 developed mucous membrane or decidua begins to secrete, 

 the os uteri becomes plugged up by this secretion, where it 

 assumes the form of elongated epithelial cells ; the cavity of 

 the uterus becomes filled with a fluid secretion, the " hydro- 

 perione " of Breschet, and in the immediate neighbourhood of 

 the ovum, the secretion consists of cells of a spherical form. 



