. Quain's elements of anatomy . e glands, which undergo a remarkableenlargement (see later) in the decidua vera, speedily disappear, and itis now well ascertained in animals, by the researches of Ercolani andTurnerj that the foetal villi do not, as was once supposed, penetrate into 782 HUMAN UTEROGESTATIOK the dilated cavities of the uterine glands, hut are sunk in cryi^ts of thedecidua which lie between the glandular orifices. jSTor is there anyreason to believe that the villi enter the uterine glands in the forma-tion of the human placenta. On the contrary, the observations ofSchroder van de
. Quain's elements of anatomy . e glands, which undergo a remarkableenlargement (see later) in the decidua vera, speedily disappear, and itis now well ascertained in animals, by the researches of Ercolani andTurnerj that the foetal villi do not, as was once supposed, penetrate into 782 HUMAN UTEROGESTATIOK the dilated cavities of the uterine glands, hut are sunk in cryi^ts of thedecidua which lie between the glandular orifices. jSTor is there anyreason to believe that the villi enter the uterine glands in the forma-tion of the human placenta. On the contrary, the observations ofSchroder van der Kolk, Kolliker, Turner and others are quite opposedto such a view. b. Structure of the Advanced Human Placenta.—After themiddle of pregnancy, the placenta forms a large discoid or lenticular mass,of from four to five inches in its larger diameter and about three-quartersof an inch in thickness, interposed in a limited space between the fcetalmembranes and the uterus. It presents a foetal and a uterine surface, the Fig. Kg. 676. DiAGKAJIMATIC KEPKESEKTATION OP A SECTION OF THE HUMAN PLACENTA NEAR THE MARGIN AT FIVE OR SIX MONTHS (sliglitly enlarged). (A. T.) am, amnion : c7i, chorion ; fi\ stems of fcetal vessels passing into two of the placentallobes in the villi of which they undergo capillary ramification ; m, muscular wall of thetiterus with divided arteries and veins; v, decidua vera; ?•, d. reflexa; s, deciduaserotina placentalis ; s, d. serotina uterina ; ds, septa of decidua passing from theserotina between the lobes, branching into their interior, and reacliing the chorion ; intheir bases are seen the maternal coiled arteries and the divided veins ; cs, circular sinus ;scJi, the subchorionic decidual layer. An attempt is made in this diagram to show theunion between the penetrating processes of reticulated decidua serotina and the villi of thelobes, the union extending in this, which is a marginal joart of the placenta, as far as thesubchorionic layer of the
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