THE STRUCTURE OF THE HUMAN PLACENTA. 61 



Dr. Reid.* I have dissected the vessels of an unopened uterus at 

 the full time in the manner adopted by Mr. Owen, by opening one 

 of the large veins over the spot to which the placenta was attached. 

 Introducing a probe as a guide, I slit open the vein with a pair 

 of scissors, and repeated the same process with the probe and scis- 

 sors whenever a branch entered the vein already opened. I gra- 

 dually passed through the wall of the uterus. In my progress, I 

 occasionally found, that when the probe was pushed along an un- 

 opened vein, its point appeared at another opening ; and as I ap- 

 proached the internal surface of the wall of the uterus, these 

 anastomoses of the veins became more numerous, the spaces which 

 they inclosed presenting the appearance of narrow flat bands. 

 At last, in introducing the probe under the falciform edges of the 

 veinous orifices, it was found to have arrived at the placental 

 tufts, which could be seen by raising the edges of the falciform 

 edges. Having passed over the falciform edges, the veinous 

 membrane suddenly passed to each side to line the great cavity of 

 the placenta. The flat bands which I have just described as the 

 spaces inclosed by anastomosing veinous sinuses, became smaller, 

 and, on entering the cavity itself, the bands were seen to have 

 assumed the appearance of threads, which passed in great numbers 

 from the vascular edges of the veinous openings, and from the 

 walls of the cavity of the placenta on to the extremities and sides 

 of the villi and tufts of the placenta. The whole mass of spongy 

 substance, that is the whole mass of tufts, were in this manner 

 perceived to be attached by innumerable threads of veinous mem- 

 brane to that surface of the parietal decidua of the placenta which 

 was covered by the veinous membrane. On proceeding deeper 

 into the substance of the placenta, I perceived that, throughout 

 its whole extent, villus was connected to villus, and tuft to tuft, 

 by similar threads of veinous membrane. Sometimes the apex of 

 one villus was connected to the apex of another. In other in- 

 stances the threads connected the sides of the villi. On minute 

 examination 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 



* Reid. Edinburgh Medical and Surgical Journal, loc. tit. 



