STRUCTURE OF HUMAN PLACENTA. 457 



and the observations of Dr. Keid.* 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 scissors 

 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 unopened vein, its point appeared at another opening ; and 

 as I approached 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 venous 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 venous 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 venous sinuses, became smaller, and, on enter- 

 ing 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 venous 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, was in 

 this manner perceived to be attached by innumerable threads 

 of venous membrane to that surface of the parietal decidua 

 of the placenta which was covered by the venous membrane. 

 On proceeding deeper into the substance of the placenta, I 

 perceived that, throughout its whole extent, villus was con- 

 nected to villus, and tuft to tuft, by similar threads of 



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



