The _placenta_ is an appendage of the chorion; it is a soft, spongy mass, constituting the principal connection between the ovum and the uterus, being destined to the hematosis and (as we suppose) to the nourishment of the fœtus. The placenta, at the termination of utero gestation, is a flattened body about an inch in thickness at the center; its shape is circular or oval, and it is from six to eight and one-half inches in diameter; its internal surface is covered by the chorion and amnion, and exhibits plainly the umbilical arteries and veins which converge to form the umbilical cord. Its fœtal portion is formed by the hypertrophied villi of the chorion, with which its circumference is continuous, and its maternal portion is continuous with the decidua, and is in fact a thickened part of that membrane. As the villi of the chorion are developed on one part of its surface, they ramify and form filaments that engraft themselves upon the uterine mucous membrane and adhere closely. At the same time there is an inverse development of the uterine vessels, which form vast numbers of loops that descend between the villi of the chorion, and extend through to the fœtal surface of the placenta. An amorphous matter is soon thrown out which unites the two parts together. The placenta is, therefore, composed of two parts, distinct in their physiological action, though they together present but one mass to our view. One part is the fœtal portion formed from the chorion; the other is the maternal portion formed from the uterine mucous membrane, of which it is a greatly thickened part. After delivery the fœtal placenta comes entirely away with the epithelial layer of the placental decidua, and the placental distribution of the maternal vessels; a portion of the maternal vessels remains attached to the uterus. The placenta may be inserted upon any part of the uterine cavity, although it is most usually near the fundus where the ovum must enter the womb. If, as is sometimes the case, it is attached at the lower part, over the orifice of the womb, it causes unavoidable hemorrhage in the later months of pregnancy. The _umbilical cord, funis, or naval string_, is the connecting link between the child and mother. It commences when the external lamina of the blastoderm with the alantois are so changed as to form a mere cord upon which the two umbilical arteries ramify, and when all these have an enveloping sheath from the amnios. It may be discerned in this state at the end of the first month; at that time the fœtal intestines may be seen to protrude beyond the umbilicus into the amnionic sheath, but the cord is then cylindrical and very small. There are progressive changes, the cord becomes simplified, the canal of the amnionic sheath is obliterated gradually at its extremity, and as the effacement proceeds towards the umbilicus the intestine is pressed back so that no hernia remains.