As the head advances through the pelvic cavity the pressure upon the nerves which pass through it gives rise to cramps in the thighs and legs. As the head passes into the vagina the walls become flabby and the canal seems to enlarge and elongate and to be prepared to yield to the pressure of the head. If an internal examination be made the head will be perceived filling the cavity, descending with each pain and receding at its conclusion—the advance ordinarily exceeding the recession, though sometimes the gain is not perceptible. When the head rests on the perineum, that offers some resistance, which seems to stimulate the uterus and abdominal muscles to greater efforts and more forcible contractions. If it be a first labor there may be at this point a little delay in its progress. But the fœtal head being forced down by the rapidly recurring pains so presses against the floor of the pelvis that it yields and becomes bulging in front, and distended, though there still is recession as the pain intermits. But adequate force is called into action; each pain gains upon the advance made by its predecessor; the vulva partially opens, and at each pain they open more and more; the resistance of the parts is finally overcome. After the perineum has given the head its proper direction in its transit, there usually comes a hard pain—forcing a loud cry from the woman—another pain succeeds immediately, which expels the head altogether from the parts; then after a short rest the uterine power is again exerted to expel the body of the child. There may be an interval of a few minutes before the pains return with sufficient force to expel the shoulders, but the child is in no particular danger; it is best to wait awhile, the nurse in the meantime making pressure with her hand over the uterus, before any traction is made on the head or shoulders. If the body is very large, however, it may be well soon to draw a little on the head or to reach with one finger into the axilla and to bring down the lower shoulders; then the rest will be delivered without any difficulty. The intense suffering of the mother is now exchanged for perfect joy or ease; there is at once a transition from extreme misery to total freedom from pain, though the labor is not yet completed. Ordinarily a few pains return before many minutes, and complete the last stage of labor—the expulsion of the placenta. Sometimes the contractions that expel the child, expel also the membranes and placenta; but more generally they are only partially detached or they may be adherent and not easily removed.