Page:Popular Science Monthly Volume 68.djvu/432

 428 it into fatty acid and glycerine. This action, according to ferment law, would continue till a mixture of fat and fatty acid in chemical equilibrium was produced. But in the intestine, absorption begins and fatty acid is removed as fast as formed, thus allowing the ferment to continue its action as long as any fat remains in the intestine. But if both fatty acid and ferment are absorbed together, then, as soon as they get inside the absorbing cell, the ferment in the presence of fatty acid only will begin its work over again, which then will be the formation of droplets of neutral fat from the fatty acid absorbed.

This view rests on the assumption that fat ferment accompanies the fat from intestine to tissue. The observers mentioned have investigated this subject. They examined a large number of fat-containing tissues and organs, and found in every case that they contained fat ferment about in the proportion that they contained fat, except that the liver contained a very active ferment out of proportion to the amount of fat in that organ.

The fat absorbed from the intestine finds its way into the lymphatics and thence to the thoracic duct, there to be mingled with the blood. Shortly after a meal if the blood serum of an animal be taken and allowed to stand a layer of fat forms on top. The serum taken some hours after a meal, on standing forms no such layer, showing that fat rapidly disappears from the blood. And here arises one of the interesting problems of fat metabolism. What becomes of fat when it disappears from the blood and what is the origin of the fat in the tissues? A very simple explanation would be that the fat of the blood is deposited in the tissue cells. Another theory, and one that has had the sanction of good authority, is that the fat in the tissues is made there from their own proteid substance.

In favor of the transformation of proteid into fat are usually mentioned the following: In the ripening of cheese, fat is increased at the expense of proteid. In certain damp soils corpses have their proteid converted into a fatty substance known as adipocere. Both of these arguments are somewhat less convincing when it is known that bacteria are the active agents of these changes. As the result of various poisons—notably phosphorus—the liver is found to contain large quantities of fat in the form of droplets in the injured cells of the organ. This has been called fatty degeneration and the protoplasm of the degenerating cells in one stage of degeneration was thought to be changed to fat. On the other hand, it is claimed that if an animal is first starved, so that fat disappears from the body, and then poisoned with phosphorous, no fat appears in the liver. There is too other evidence of an experimental nature to show that the fat of fatty degeneration is fat transported from the usual depots of fat and simply