=Manner of Performance of Digestion.=--The organs situated in what is called in medical language the abdomen, have in the child no other duty to perform than such as subserve the processes of digestion and nutrition. The saliva secreted by the appropriate glands in the mouth, mixing with the food, facilitates the further changes which take place in the stomach. In the stomach the food is acted on and dissolved by the gastric juice or pepsin, which is poured out by an almost infinity of minute tubes, or follicles as they are termed. When the stomach has done its work, its contents in a semi-fluid state pass into the small intestine, and mix there with the bile, the secretions from the intestines themselves, and with those of the large gland, the pancreas (in culinary language known as the sweetbread), which seems to have the special power of dissolving fatty matters. As the food, thus acted on, travels along the intestines, whose constant movement facilitates the passage of their contents from above downwards, its elements are taken up, partly by the blood-vessels, partly by innumerable small vessels, called absorbents from their power of imbibing fluids, and lacteals, from the milky hue of the fluid within them when first absorbed. The fluid taken up by the blood-vessels is conveyed to the liver; that taken up by the absorbents to the mesenteric glands, and in these organs further changes take place in it, which fit it to be received into the mass of the circulating fluid. With this it is carried to the right side of the heart, and thence to the lungs and, lastly, from them to the left side of the heart, whence it is distributed, the great life and health giver, to the rest of the body. The useless inconvertible material, leaving every available element behind, is got rid of, either in a solid form by the bowels, or in a fluid form by the kidneys; and thus as long as life lasts there goes on more or less perfectly the wonderful process of constant change, of constant renewal, and during childhood and youth, of constant increase of size and stature.