=Walking on all fours= is violent exercise and is taken up very gradually. Some women are able to attempt it on the first day out of bed, if they have been taking the other exercises regularly, but as a rule it is not started until the second, third or fourth day after getting up. The clothes are free from all constrictions, pajamas being very satisfactory; the knees are held stiff and straight with the feet widely separated, to allow a rush of air into the vagina, and the entire palmar surface of the hands rests flat on the floor. (See Fig. 40.) The patient starts by taking only a few steps each morning and evening, gradually lengthening the walk to five minutes twice daily and continuing it for about two months. It is believed that as the young mother walks in this position the uterus and rectum rub against each other, producing something the same result as would be obtained if it were possible to massage them, the effect of this being to promote involution, which will be explained later, and lessen the tendency toward constipation and uterine misplacement. [Illustration: FIG. 39.—Knee chest position. ] The general purpose of these exercises, as a whole, then, is to strengthen the abdominal muscles, thus helping to prevent a large, pendulous abdomen; to increase the convalescing mother’s general strength and tone just as exercise benefits the average person; to promote involution (See page 134); to prevent misplacement of the uterus and in a measure to relieve constipation. In order that the exercises may accomplish these much-to-be-desired ends, the doctors who advise them feel that it is important for them to be taken with moderation and judgment; started slowly; increased gradually and constantly adjusted to the strength of the individual mother. [Illustration: FIG. 40.—Walking on all fours. ] Otherwise they may do more harm than good. Concerning the changes that take place in your body during the puerperium, the ones that will interest you particularly are: (1) the shrinkage in the size of your uterus and its gradual descent into the pelvis where it was before the baby began his life within it; (2) the production of milk by your breasts; (3) a loss of body weight. =The Uterus.= Immediately after delivery the uterus weighs about 2 pounds; is from 7 to 8 inches high; about 5 inches across and 4 inches thick. The top of the uterus, or fundus, may be felt just below the navel and the inner surface where the placenta was attached, is raw and bleeding. At the end of six or eight weeks the organ has descended into the pelvic cavity and resumed approximately its original position and size and its former weight of 2 ounces. This return of the uterus to practically its pre-pregnant state is called _involution_ and in the interest of your immediate recovery and future health it is important that this shall progress normally.