The wide part of the pelvis above the inlet is called the upper, or _false pelvis_, while the smaller cavity below is known as the _true pelvis_. During the early part of pregnancy the baby lies in the true pelvis, but as pregnancy advances and he grows larger, he pushes up through the inlet into the larger pelvis where he remains until he is born. When that time comes he must pass down through the inlet again on his way into the world. If this opening is about the usual size and shape and the baby is of an average size, he will usually pass through with comparatively little trouble. But if the inlet is smaller than normal or of an unusual shape, it may be difficult, or even impossible, for the head of a normal-sized baby to pass through without the doctor’s assistance. You can see how important it is, therefore, for the doctor to know beforehand about the size and shape of the pelvic inlet, since it enables him to plan to help with the birth, if necessary, thus saving mother and baby from exhausting themselves in trying to do the impossible. In the old days many mothers and babies were injured, and sometimes even lost their lives, because doctors did not know about measuring the pelvis and planning ahead of time for a difficult labor. But now they know how to make things easier and safer. It is worth mentioning here that proper care during infancy and childhood, with proper food, fresh air and exercise, helps to promote normal development of the pelves of little girls, and this in turn tends to make childbirth normal for these children when they grow up and are ready to have babies of their own. =The Generative or Reproductive Organs.= The pelvis is an interesting structure but not nearly so interesting as the generative organs which lie within it: the _uterus_ (or womb), _tubes_ and _ovaries_. These, with the vagina, are often called the _internal genitalia_ because they are inside the body. The pelvis practically remains rigid and inactive throughout pregnancy and labor, but the ovaries and the uterus are constantly active and are concerned with an undertaking which is so utterly amazing that it is far beyond our powers of understanding. We can only look on and wonder. [Illustration: FIG. 2.—Drawing showing the structure and relation of the female generative organs, as viewed from the side. (Drawn by Max Brödel. Used by permission of A. J. Nystrom and Co., Chicago.) ]