Page:Popular Science Monthly Volume 68.djvu/433

Rh deposited in the degenerating cells. The fat of different animals consists of different proportions of the three common fats, olein, palmitin and stearin. But for each animal the proportion in which the three fats enter into its fatty mixture is fairly constant. Recall the difference between beef and mutton tallow and lard. This proportion of fats being fairly constant for an animal species, it does not change with every change of diet. But if an animal be starved for a time and then fed exclusively on a particular fat, such as some vegetable fat never normally found in the animal, the fat used can be demonstrated as present unaltered in the tissues. The question then of the origin of tissue fat is still somewhat uncertain. It seems safe to say that the fat of the food can be deposited unaltered in the tissues, but that all the fat found in the tissues has had its origin in fatty food is certainly not the case; much of it is made from carbohydrate and some of it may be made from proteid.

Turning to the question of the disposal of fat in the body, we may say that it is completely burned in the tissues and has as its end products carbonic acid and water.

A moderate amount of fat in many tissues, especially the subcutaneous connective tissues, the omentum and tissue about the kidney, is normal, and serves as a store of energy, as a protective covering to the body and to retain the body's heat. But there are many persons in whom this amount is excessive, that is, in no way proportioned to their needs. In seeking an explanation of these cases we are at once struck with individual differences. For instance, one sees persons over whose bodies there is a uniform thick layer of fat; they are of florid complexion and many of them active persons. The term corpulent applies to them better than obese, since their bodies exhibit both an increase of fat and of protoplasm and their blood is of normal specific gravity. In the presence of a good digestion and abnormal appetite, they daily consume more food energy than the daily expense of energy requires. The excess is laid away as tissue proteid and fat. A moderate diminution in food taken with some increase in exercise would rectify the condition. But it is almost a waste of words to tell a man to eat less in the presence of an excellent appetite and digestion.

There are other persons in whom the picture is quite different. The fat is not uniformly distributed, but is largely abdominal, the arms and legs being little enlarged; they are pale, and blood examination reveals anemia and diminished specific gravity of blood. Herter calls attention to the rather striking parallel between this condition and diabetes. In diabetes there is an excess of sugar in the body tissues. This has been shown not to be due to any increase in sugar manufacture, but to