7(30 THE PLACENTA. 



be traced from their attachment at the under surface of the chorion to 

 their termination near the uterine surface of the placenta. The ana- 

 tomical disposition of the placental sinuses is more difficult of examina- 

 tion. During life, and while the placenta is still attached to the uterus, 

 they are filled, of course, with the blood of the mother, and occupy fully 

 one-half the mass of the placenta. But when the placenta is detached, 

 the maternal vessels belonging to it are torn oif at their necks (Fig. 

 274, c, c, c, c), and the sinuses, being then emptied of blood by the com- 

 pression to which the placenta is subjected, are apparently obliterated ; 

 and the foetal tufts, falling together and lying in contact with each 

 other, appear to constitute the whole of the placental mass. The ex- 

 istence of the placental sinuses, however, and their true extent, may be 

 demonstrated in the following manner. 



If we take the uterus of a woman who has died undelivered at the 

 full term or thereabout, and open it in such a way as to avoid wounding 

 the placenta, this organ will be seen remaining attached to the uterine 

 surface, with all its vascular connections complete. Let the foetus be 

 now removed by dividing the umbilical cord, and the uterus, with the 

 placenta attached, placed under water, with its internal surface upper- 

 most. If the end of a blowpipe be then introduced into one of the 

 divided vessels of the uterine walls, and air forced in by gentle insuffla- 

 tion, we can easily inflate, first, the vascular sinuses of the uterus, and 

 next, the deeper portions of the placenta ; and lastly, the bubbles of air 

 insinuate themselves every where between the foetal tufts, and appear in 

 the most superficial portions of the placenta, immediately underneath 

 the transparent chorion (a, a, Fig. 274) ; thus showing that the pla- 

 cental sinuses, which freely communicate with the uterine vessels, occupy 

 the entire thickness of the placenta, and are equally extensive with the 

 tufts of the chorion. We have verified this fact in the above manner, 

 on six different occasions, and in the presence of Prof. C. R. Oilman, 

 Prof. Geo. T. Elliot, Prof. Henry B. Sands, Prof. T. G. Thomas, Dr. T. 

 C. Finnell, and various other medical gentlemen of New York. The 

 same thing has been done by Prof. A. Flint, Jr., 1 with a similar result. 



If the placenta be detached and examined separately, it will be found 

 to present upon its uterine surface a number of openings, which are ex- 

 tremely oblique in position, and bounded on one side by a very thin 

 crescentic edge. These are the orifices of the uterine bloodvessels, 

 passing into the placenta and torn off at their necks, as above described ; 

 and by carefully following them with the probe and scissors, they are 

 found to lead at once into extensive empty cavities (the placental 

 sinuses), situated between the foetal tufts. These cavities are filled 

 during life with the maternal blood ; and there is every reason to believe 

 that before delivery, while the circulation is going on, the placenta is at 

 least twice as large as after it has been detached and expelled from the 

 uterus. 



1 Flint, Physiology of Man. New York, 18^4, vol. v. p. 382. 





