Page:Popular Science Monthly Volume 68.djvu/434

430 an inability of the body to oxidize the sugar. In diabetes the excess of sugar then is removed by the kidneys. In obesity the fat is not removed, but accumulates in adipose tissue. The explanation of both conditions would be an inability of the body cells to oxidize these substances. Herter states the points of similarity of the conditions thus:

 1. Diminished oxidation of both materials. 2. The two conditions are frequently associated. 3. In each case the defective utilization of nutritive materials is more or less closely associated with substances produced by certain glands. It has been clearly proved that disease of, or removal of, certain groups of cells imbedded in the pancreas, known as the 'islands of Langerhans,' cause the appearance of sugar in the urine. And no doubt remains that many of the cases of diabetes are primarily disease of the pancreas. On the other hand, obesity may depend on the suspension of function of other glands. The removal of the sexual glands is commonly, though by no means invariably, followed by the laying on of fat. This fact is taken advantage of by the poultryman in supplying capon for the market. Members of the human species may be similarly affected.

But the gland showing the most intimate relation between its function and obesity is the thyroid. This gland is situated in the neck, on either side of the trachea. Its enlargement constitutes goitre. Its absence or disease result in cretinism and myxœdema. When portions of the dried gland of a sheep are mixed with the food of the normal or obese individual marked bodily changes result. The results of thyroid feeding in men and animals have been well summarized by Richardson. In the first place, there is a marked increase of oxygen consumption and carbonic acid excretion, that is, some constituent of the gland promotes oxidation. This is accompanied by a loss of weight.

The oxidation is not, however, selective of the fats alone, for most observations have shown that there is an increase in the elimination of nitrogen. This would mean that proteid is being consumed as well as fat. If an animal was in nitrogenous equilibrium at the beginning of the experiment, we should expect it to be considerably weakened by its consumption of its own protoplasm. If, however, the nitrogenous food is increased, while thyroid substance is being fed to the animal the condition of nitrogenous equilibrium can again be restored, and the subsequent loss of weight will be due chiefly to the oxidation of fat. The above statement makes it clear that the question of the amount of fat in any individual is a very complex one, depending on such a variety of factors as condition of digestion, appetite, character and quantity of food, amount of exercise and the proper working of a number of body glands.