placebo (plas-e'bo)

A make-believe medicine; something administered for its efthan fectbecause on the patient's it is of imagination medicinal rather value. [The first person sing. fut. ind. of Lat, placere, to please. Lit., / will please placenta (pla-sen'tah). Syn.: he par uterinum. The afterbirth; an organ which during fetal life, in nearly all mammals, performs the function of aerating the blood of the fetus by providing the you.'] mechanism nece ary to a direct interchange of gases between the fetal and the maternal blood; consisting of a maternal portion (see maternal p.) and a fetal portion (see fetal p.) closely interwoven with each other, the whole organ, thus doubly constructed, being intimately connected with the internal organism by its implantation upon the interior of the uterine wall on the one hand and connected with the fetal circulation by the umbilical cord on the other, annular p. See zonary p. basal p., basilar p. A free central p., a p. in which the ovules are borne on a column which rises free from the bottom of the ovary, battledore p. That form of insertion of the umbilical cord into the margin of the p. in which it spreads out so as to resemble a battledore, bell-shaped p. See domelike p. circinate p. A cup-shaped p. cordiform p. A p. having a marginal indentation giving it a heart shape, deciduate p. A p. of which the maternal portion comes away at delivery, diffused p. See p. diffusa, p. membranacea, and villous p. discoid p. That variety of p. in which, as in the human subject, it constitutes practically one ma , circumscribed in outline and more or le circular in form, di eminated p. See villous p. domelike p. That variety of p. in which the chorionic villi persist at the upper pole of the chorion, and for some distance around that point, but disappear from the lower pole, double p.