Personal hygiene and physical training for women

by Anna M. Galbraith

The succus entericus is the secretion of the glands of Lieberkühn. It contains quite a number of enzymes, including four which act on carbohydrates, namely, amylase, maltose, lactase, and invertase; the proteolytic enzyme is erepsin, which seems to supplement the action of trypsin. It has no action on native proteins except casein, but it breaks down proteoses and peptones into amino-acids.

In other words, the discovery of erepsin in the succus entericus and its effects has led to the now almost generally accepted view that the digestion of the proteins is carried further than the stage of proteoses and peptones; in fact, that this enzyme hydrolyzes them into amino-acids, in which form they are taken up by the cells of the intestinal mucous membrane.

The Absorption of Food from the Intestines.—It was formerly believed that the main stream of the nutrient passed out of the intestines through the lacteals and thoracic duct into the circulation. But it is now known that only the fats take this course, and that the dissolved proteins, carbohydrates, some fats and salts find their way into the circulation through the portal system and the liver.

The blood contains a constant proportion of serum-albumin and serum-globulin, which are constructed out of the amino-acids resulting from the digestion of protein foods. The reconstruction of proteins takes place chiefly in the cells. Fuchs believes that the amino-acids from the food are carried to all the tissues; and that the cells of the muscles and glands pick out from the blood the “building stones” necessary for the construction of their special proteins.

Fat is absorbed for the most part in the form of an emulsion and as a solution of soap. Only about 60 per cent. of the fat in the food is absorbed by the lacteals; the remaining 40 per cent. gets directly into the blood. The fat is carried directly by the blood-stream to the tissues all over the body; it is oxidized in the tissues to produce heat and energy; what is not immediately used for this purpose is stored up in the cells for future use.

Carbohydrates.—Practically all of the carbohydrates digested are absorbed in the form of sugar. The absorption takes place more rapidly in the upper than in the lower bowel. A portion of the ingested carbohydrates is destroyed in the alimentary canal by bacteria, whose enzymes transform them into various acids and gases.

The Absorption of Sugar.—The sugars pass into the blood through the portal circulation, and not through the lymphatic vessels. The question is, Where does sugar go after it gets into the blood? The proportion of sugar in the general circulation is not greater after a meal than before it. It is necessary that there should be some means of storing it, for it cannot all be immediately used for the production of energy. Is it stored as glycogen? Bunge believes that a considerable amount of carbohydrate is stored as fat, since the total amount of glycogen in the liver never exceeds 150 grams, and there is a similar store in the whole mass of muscles. It is evident, therefore, that only a small proportion of carbohydrates is laid down as glycogen, and we must assume that the greater part of it is converted into fat. That fat accumulates in the body on a purely carbohydrate diet is proved beyond a doubt, and the formation of fat from sugar is considered proved by experimental evidence.

Sugar is an important source of energy for the muscles, and provision is made for a sufficiency of it always to be in the blood circulating through them, and the storehouse from which it is derived is the liver. When the liver and muscles contain enough glycogen to keep the blood supplied with it, the excess of sugar is converted into fat, and is reconverted into sugar when there is a demand for it.

Mechanics of Digestion in the Intestines.—The intestinal movements, like those of the stomach, have recently been studied by means of the x-rays. There are three kinds: A pendulum-like motion, consisting of a gentle, swaying, rhythmic movement occurring in all parts of the intestines. These movements do not affect the whole of the gut at one time, but occur in successive segments of it, and are more obvious in those parts which are distended with food, at a period of three or four hours after a meal. They are most energetic in the upper and least so in the lower part of the gut, and proceed from above downward with the course of the food.

The movement consists in lengthening and narrowing, followed by shortening and widening, of the canal; the contraction involves both the longitudinal and circular muscular coats, and in the course of its progress divides the bowel into many segments. This movement breaks up the food, sways it backward and forward, diffuses the digestive fluids through it, and drives chyle into the lacteals.