Obstetricians divide a parturition into three stages. In most primiparae and many multiparae there is a prodromal stage, in which false labor pains (_dolores praesagientes_) are the most evident symptom. When the real labor sets in there are rhythmic uterine contractions about every fifteen minutes, which cause pain to the woman by the pressure of the fetus on the uterine nerves--_dolores praeparantes_. From the time the pains become rhythmic, and are effective in dilating the neck and mouth of the womb, until the mouth of the womb is completely stretched and flush with the vaginal wall, thus completing the continuous parturient canal, is the first stage of labor. The fetal enveloping membranes (the "bag of waters") usually rupture at the end of this stage, but sometimes the bag bursts before the end, or as late as the second stage of labor. The first period is the stage of dilatation. The second stage extends from the end of the dilatation until the expulsion of the child is completed. This is the stage of expulsion. The third stage lasts from the delivery of the child until after the expulsion of the placenta and membranes and the retraction of the uterus has ended--the period of the afterbirth. Normal parturition is always painful to the woman. As the labor progresses the pains gradually grow more intense, and the interval between them shorter. After a few hours the pain is strong enough to cause the woman to cry out, but there is a great variety in the endurance of these pains, as the women's characters differ. Neurotic women begin to scream and act hysterically even in the early part of the first stage. When the pains are fully developed each lasts about half a minute. In most cases the infant comes out head first, but almost any part of its body may present. Before the advancing child part of the _liquor amnii_ within the fetal enveloping membranes is forced down into the neck of the womb, and causes dilatation. In primiparae especially the bag of waters may rupture prematurely and thus cause what is called a dry labor, which is commonly tedious and painful. Often operative interference is required in dry labors. In the second stage the pains are stronger, recur every two or three minutes, and are expulsive. The woman then strives to expel the child. She strains violently with the abdominal muscles--literally labors; her pulse is high, the veins of her neck stand out, her face is turgid, and her body is covered with sweat. When at last the head of the child is driven out the woman feels as if she were being torn asunder in the _dolores conquassantes_. The pain is so great that the woman may faint from it, but that is not the rule. After a pause the shoulders are forced out, and then the trunk in one long convulsive effort. The umbilical cord is tied and cut, and the child is born.