=Corpora Lutea.= After the Graafian follicle has burst and the ovum has been pushed out, the cavity that is left does not remain empty and functionless; there is a further process going on there; there is a growth of cells, of a yellowish color, and the follicle becomes filled with a yellowish body, which on account of its color is called the _corpus luteum_ (plural--corpora lutea; luteum in Latin--yellow, corpus--body). This corpus luteum grows in size until it sometimes occupies as much as one-third of the ovary. But there is considerable difference between the corpora lutea of non-pregnant and pregnant women. Up to the end of about a month the corpora lutea are the same, but after that the corpus luteum of the non-pregnant woman begins to get smaller, to shrink, so that at the end of two or three months it is reduced to a small scar and later cannot be noticed at all. The corpus luteum of the pregnant woman keeps on increasing until the end of the second month, remains about the same size until the end of the sixth month, and only then begins gradually to diminish. The corpus luteum of the non-pregnant woman, that is, the one following menstruation, is called false corpus luteum; the corpus luteum following pregnancy is called a true corpus luteum. The corpus luteum acts like a gland and elaborates a secretion which has an influence on the circulation in the uterus and on menstruation. It probably possesses other properties, with which we are not yet quite familiar. The corpora lutea of various animals are now prepared in powder or tablet form and used in medicine in the treatment of certain diseases of women. SUBCHAPTER B FUNCTION OF THE OTHER GENITAL ORGANS =Function of the Fallopian Tubes.= The function of the Fallopian tubes or oviducts as they are sometimes called is to catch the ovum as it bursts through the ovary and to conduct it from the ovary into the uterus. It is while the ovum is in the narrow lumen of the tube that the spermatozooen which has travelled up from the uterus usually finds it, and it is in the tube, near its entrance to the womb, that impregnation usually takes place. After the ovum is impregnated or fecundated, it slowly moves down to the uterus, where it attaches itself and remains and grows for nine months, until it is ready to come out and start an independent life.