458 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS. 



venous membrane. Sometimes the apex of one villus was 

 connected to the apex of another. In other instances the 

 threads connected the sides of the villi. On mmute examina- 

 tion these threads were found to be tubular, and the mem- 

 brane of which they were formed was seen to be continuous 

 in one direction with the lining membrane of the vascular 

 system of the mother, and in the other with the external 

 membrane of the tufts of the placenta, and passing from one 

 tuft, or set of tufts, on to another, so as to form the central 

 containing membrane of the bag of the placenta. These 

 threads, as well as their cavities, are somewhat funnel-shaped 

 at each extremity. The funnel-shaped portions of the cavities 

 of threads, and, in some instances, the whole length of the 

 tube, were found to be full of cells, which were continuous in 

 the one direction with the parietal decidua of the placenta, 

 and in the other with the external cells of the placental villi.* 



This observation led me at once to perceive the real signi- 

 fication of the external cells of the placental tufts. I saw 

 that this great system of cells was a portion of the decidua, 

 all but cut off from the principal mass by the enormous 

 development of the decidual vascular network, but still con- 

 nected with it by the minute files of cells which fill the 

 cavities of the placental threads. 



This system of cells, the external cells of the \dllus, with 

 the external membrane, are portions of the decidua, and, un- 

 like the other elements of the placental tufts, belong to the 

 organism of the mother. These cells, with their membrane, I 

 name the central division of the placental decidua, to dis- 

 tinguish it from the other portion formerly described, and 

 which I have already called the j)arietal division of the 

 placental decidua. 



1. My observations have confirmed the statements of 



* These are the reflections of the venous membrane of the mother, ile- 

 .scribed by Dr. Reid. 



