UTERINE PREGNANCY.
There are many who manifest a laudable desire to understand the physiology of conception, the changes which take place, and the order of their natural occurrence. When impregnation takes place at the ovaries or within the Fallopian tubes, there is exuded upon the inner surface of the womb a peculiar nutritious substance. It flows out of the minute porous openings surrounding the termination of the Fallopian tube within the uterine cavity, and, thus, is in readiness to receive the germ, and retain it there until it becomes attached. Undoubtedly, the germ imbibes materials from this matter for its nurture and growth. This membranous substance is termed the decidua, and disappears after conception is insured. Two membranes form around the embryo; the inner one is called the amnion, the outer one the chorion. Both serve for the protection of the embryo, and the inner one contains the liquor amnii, in which it floats during intra-uterine life. Immediately after conception, the small glands in the neck of the uterus usually throw out a sticky secretion, filling the canal, or uniting its sides, so that nothing can enter or leave the uterine cavity.
The fertilized ovum rapidly develops. After its conception it imbibes nourishment, and there is a disposition in fluids to pass into it, through its delicately-organized membranes. If this process is not involuntary, it is, at all events, at the convenience and use of the developing germ. After three months the embryo is termed the foetus. Its fluids are then so much more highly organized, that some of them are tinged with sanguine hues, and thenceforward acquire the characteristics of red blood. Out of red blood, blood-vessels are formed, and from the incipient development of the heart follow faint lines of arteries, and the engineers of nutrition survey a circulatory system, perfecting the vascular connections by supplementing the arteries with a complete net-work of veins and capillaries.