Recognition of these dangers, and the possibility of preventing them, is responsible for the present custom of obstetricians to watch over their patients during the puerperium. This is in sharp contrast to the old practice of the doctor’s visiting the puerperal woman only when there was a complication so apparent that he was summoned. The precautions and the care which the doctor takes of his patient after delivery involve intelligent and watchful nursing. In order to give this the nurse must understand something of the normal physiology of the puerperium, just as she did in pregnancy and labor. Otherwise she may not be able to distinguish evidences of normal changes from symptoms of complications. =Involution.= Considerable attention is centred in the remarkable atrophic changes that take place in the uterus during the puerperium, for it is upon their being normal that the patient’s recovery and future well-being so largely depend. Immediately after delivery the uterus weighs about two pounds; is from seven to eight inches high; about five inches across and four inches thick. The top of the fundus may be felt above the umbilicus, and the inner surface, where the placenta was attached, is raw and bleeding. At the end of six or eight weeks the uterus has descended into the pelvic cavity and resumed approximately its original position and size, and its former weight of two ounces; a new lining has developed from the few glands which have not been cast off in the discharges. This rapid diminution in the size of the uterus is termed involution and is accomplished by means of a process of self-digestion or _autolysis_. The protein material in the uterine walls is broken down into simpler components which are absorbed and eventually cast off largely through the urine. This change and absorption of uterine tissues is similar to the resolution that takes place in a consolidated lung in pneumonia. Since satisfactory involution is necessary to the patient’s future health, its progress should be watched with deep concern and interest, and all possible effort made to promote it; firm consistency of the uterus and a steady descent into the pelvis and normal lochia being the chief evidences of satisfactory involution. There is evidently a close relation between the functions of the breasts and of the uterus during the puerperium, and as a rule involution accordingly progresses more normally in women who nurse their babies than in those who do not. The so-called “after-pains” are also affected by nursing, being more severe as a rule when the baby is at the breast than at other times. These pains are caused by the alternate contractions and relaxations of the uterine muscles and are more common in multiparæ, than in primiparæ, because the muscles of the former have somewhat less tone than the latter and therefore tend to relax, and then contract, whereas the better muscle tone of the primipara tends to keep the uterus steadily contracted.