When in any individual the weight varies rapidly or slowly, it is nearly always due, for the most part, to a change in the amount of adipose tissue stored away in the meshes of the areolar tissue. Almost any grave change for the worse in health is at once betrayed in most people by a diminution of fat, and this is readily seen in the altered forms of the face, which, because it is the always visible and in outline the most irregular part of the body, shows first and most plainly the loss or gain of tissue. Fatty matter is therefore that constituent of the body which goes and comes most easily. Why there is in nearly every one a normal limit to its accumulation we cannot say, nor yet why this limit should vary as life goes on. Even in health the weight of men, and still more of women, is by no means constant, but, as a rule, when we are holding our own with that share of stored-up fat which belongs to the individual we are usually in a condition of nutritive prosperity, and when after any strain or trial which has lessened weight we are slowly repairing mischief and laying by fat we are equally in a state of health. The loss of fat which is not due to change of diet or to exercise, especially its rapid or steady loss, nearly always goes along with conditions which impoverish the blood, and, on the other hand, the gain of fat up to a certain point seems to go hand in hand with a rise in all other essentials of health, and notably with an improvement in the color and amount of the red corpuscles. The quantity of fat which is healthy for the individual varies with the sex, the climate, the habits, the season, the time of life, the race, and the breed. Quetelet[3] has shown that before puberty the weight of the male is for equal ages above that of the female, but that towards puberty the proportional weight of the female, due chiefly to gain in fat, increases, so that at twelve the two sexes are alike in this respect. During the child-bearing time there is an absolute lessening on the part of the female, but after this time the weight of the woman increases, and the maximum is attained at about the age of fifty. Dr. Henry I. Bowditch[4] reaches somewhat similar conclusions, and shows from much more numerous measurements of Boston children that growing boys are heavier in proportion to their height than girls until they reach fifty-eight inches, which is attained about the fourteenth year. Then the girl passes the boy in weight, which Dr. Bowditch thinks is due to the accumulation of adipose tissue at puberty. After two or three years more the male again acquires and retains superiority in weight and height.