=The Ovaries.= Very near and a little below the flaring, open ends of the tubes are the ovaries, the sex glands of the female. There is one on each side, held in place by ligaments and they are about the size and shape of almonds. In the ovaries are embedded the _ova_, or eggs, the female germ cells which are concerned with producing the baby and also with the function of menstruation. [Illustration: FIG. 4.—Diagram of human ovum. ] Just a word about what is meant by “a cell.” It is simply a tiny mass of jelly-like substance, called protoplasm, contained in a thin membrane or skin and is so small that it can be seen only through a microscope. In its unmatured state the ovum is a single cell, about ¹⁄₁₂₅ of an inch in diameter. In the protoplasm there is a spot called the nucleus and within this a smaller one called the nucleolus, or the germinal spot. These are long names and you need not remember them unless you want to, but glance at Fig. 4 which shows an ovum and you will see that in its general structure it is much like a hen’s egg, for the latter has a yolk within the white and on the yolk a tiny speck or germinal spot. The formation of each woman’s full quota of ova, fifty thousand or more, is probably complete at the time of her birth. =The vagina= is a muscular tube, or passage way, leading from the outside of the body to the cervix, which you will remember is the lower part of the uterus. The vagina slopes upward from its opening and instead of meeting the cervix evenly it meets it almost at right angles and encases it like a sheath for about half an inch. Fig. 2 shows how these organs would appear if we were looking at them from the side. =The Bladder.= If you will glance again at Fig. 2, you will see that just in front of the vagina there is a tiny passage leading up to a sac which also is in front of the vagina, and since in this picture it is practically empty, it lies below the uterus. This sac is the bladder and you can readily understand that as the uterus enlarges during pregnancy, it presses upon the bladder and this pressure on the outside gives the same sensation as is produced by pressure from the inside when the bladder is filled with urine. That is why the expectant mother has such a constant desire to urinate during the early weeks of pregnancy, before the uterus pushes up into the abdomen, and also during the later weeks, as well as during labor, when the bladder is being pressed upon by the baby’s head. =The Rectum.= In the same picture you will see the rectum which lies just behind the uterus and vagina and which terminates in the _anus_. Between the rectum and the vagina is a thick triangular mass of muscle, called the _perineum_, which practically forms a floor to the pelvis, the bony basin without a bottom.