CONCEPTION OR IMPREGNATION takes place by the union of the male sperm and female germ. Whether this is accomplished in the _ovaries_, the _oviducts_ or the _uterus_, is still a question of discussion and investigation by physiologists. The _ovum_, or egg, matures and is taken up by the fimbriated extremities of the oviducts at the time of menstruation. To reach the outer world it must pass the length of the oviducts, the cavity and canal of the uterus and vagina. The fructifying principle of the semen consists of zoosperms, which under strong magnifying powers are seen to be filaments endowed with power of propulsion. Once entering the uterine cavity there is no reason why they should not be able to pass into the oviducts or even to reach the ovaries. The probabilities are impregnation can take place at any point in the generative tract, providing the ovum and sperms come in contact while they still live. It is pretty well proven that the ovum after maturing and being dislodged from the ovaries may retain its life from six to eight days, and also be that length of time in making its exit from the uterus. That the sperms are viable, also, for some days, if retained in their own element at a certain temperature, has been established quite definitely. With many women the ovum passes off within twenty-four or forty-eight hours after menstruation begins. Some, by careful observation, are able to know with certainty when this takes place. It is often accompanied with _malaise_, nervousness, headache, or actual uterine pain. A minute substance like the white of an egg, with a fleck of blood in it, can frequently be seen upon the clothing. Ladies who have noticed this phenomenon testify to its recurring very regularly upon the same day after menstruation. Some delicate women have observed it as late as the fourteenth day. NOURISHMENT AND DEVELOPMENT OF THE EMBRYO.--There are three distinct periods of nutrition in the uterine development of the human being: First--Yolk nutrition. Second--Tuft nutrition. Third--Placental nutrition. The period of yolk nutrition in the human is brief and probably variable. The minute size of the egg renders it impossible for it to furnish nutriment for any length of time, as is the case with the embryo of the fowl. From five to eight days after conception takes place, a membrane is formed around the ovum, called the chorion. Outside of this is still another membrane attaching itself to the womb. The internal surface of the chorion is supplied with villi or tufts resembling mulberry seed. Through these the embryo receives its nutrition, until at the close of the second month, from these tufts the _placenta_, or after-birth, begins to be developed. This is attached to some portion of the uterus, usually the upper lateral portion.