Dietary reforms should probably not be in the line of new kinds of diet, but in the line of the moderate, abstemious use of any wholesome mixed diet and its thorough mastication. The most important principle in the choice of diet is to choose one that appeals to the appetite. If one craves meat, let him get it; if he craves milk, or eggs, or cheese, or any particular fruit or vegetable, then let him have this food which he craves. But when he has this longed-for food placed before him, his opportunity for self-restraint has arrived. If he gormandizes on the food he will tax beyond the limit his digestive powers and all those functions which serve the digestion, and greatly embarrass his general activity. If he eats very moderately of this food, chewing it as described above, he will find after twenty or thirty minutes that he has completely satisfied his appetite from a surprisingly small amount of the food. The keen appetite and relish with which he eats the food is the strongest factor in the secretion of the digestive juices. These copious digestive juices quickly perform their function and within thirty minutes after such a meal the individual is ready to enter upon the strenuous duties incident to modern life.

Under the head of nitrogenous foods we will discuss only two classes, lean meats and eggs. Many writers place milk in this group and call the group "animal foods." In our classification milk is grouped with the carbo-nitrogenous foods because its content of nitrogenous foods is small in proportion to the carbonaceous foods, and further its content of nitrogenous food is not sufficient to justify the use of milk as an especially important source of proteins. Cheese, a milk product, is, of course, largely protein, representing as it does the coagulated proteins of the milk, pressed and cured. The use of milk as the sole food of young mammals during the first stage of their life after birth, and its extensive use as an invalid food, where for days and even weeks it may be almost the only food taken, justifies the classification of milk as a complete food along with legumes, cereals, and nuts.

In our nitrogenous foods, then, we will consider only meat and eggs. When lean meat and eggs are introduced into the alimentary canal, after being reduced to the finest possible state of division in the mouth, they are passed into the stomach, where they are largely transformed, under the influence of the acid gastric juice, into peptones. If they have been properly masticated this peptonizing process is a rapid one, probably consuming not over two or three hours at most. Any portions of the meat proteins not changed in the stomach will be changed by the trypsin of the pancreatic juice. In the condition of peptones the proteins are absorbed and changed back to proteins, in the epithelium of the small intestine, and passed into the blood as serum albumin and serum globulin. In this form they circulate as a part of the blood and lymph until absorbed from these circulating fluids by the active cells of the tissues for use in building and repairing these cells.

It is already stated above that whenever the amount of proteins taken into the body falls short of the amount required, equilibrium is disturbed and a wasting process begins. A question of equal importance is: What happens when the amount of protein ingested exceeds the amount needed for growth and repair?

The proteins in excess of the needs of the tissues for growth and repair are quickly oxidized. This oxidation yields energy in the form of heat and muscular work, the same as is true in the oxidation of other foods. Incident to this oxidation there appear numerous waste products. When carbonaceous foods are oxidized carbon dioxid is the waste product. When nitrogenous foods are oxidized the waste products consist of carbon dioxid, together with sulphates, phosphates, and numerous nitrogenous compounds. All of these, excepting the carbon dioxid, can pass out of the body only by way of the kidneys, except a small proportion that goes out through the bile.

It is easy to understand that excessive use of nitrogenous foods may readily overwork the organs which excrete nitrogenous waste products. Rightly interpreted, the recent advances of animal nutrition point not toward vegetarianism, but rather toward moderation and mastication.

Class 1. Lean meats include not alone the muscle tissues of beef, mutton, pork, but the muscle tissues of edible animals of all classes. Besides these more common sources of lean meat, there are the domestic fowls: chickens, ducks, geese, turkeys, pigeons, and guinea fowl. Among the game - the four-footed beasts - may be named the deer, bear, elk, moose, mountain sheep, antelope, rabbit, coon, and opossum. And among game birds: wild turkeys, geese, ducks, pigeons, quail, snipe, partridge, grouse, etc.

Fish is another important source of lean meat. Less important are the sea foods, sometimes called shellfish. Among these may be named the lobster, crab, shrimp, oyster, and clam, the edible portions of all these being the muscle tissue, and in the case of the oyster and clam not alone the muscle tissue, but the whole soft body, including the connective tissues, digestive organs, and gills. In glancing at the table showing chemical analysis of meats, note that the proteins of fresh meats range from about fifteen to twenty-five per cent of the whole, while the carbonaceous foods are represented by fats alone, and these range in proportion from one or two per cent up to nearly forty per cent.

Lean meat from all of the sources above enumerated consists of muscle tissue, together with a certain amount of connective tissue, blood-vessels, nerves, and lymphatics. The muscle tissue is essential and is the contractile tissue of the body. The other tissues are incidental, the connective tissue forming the sheath of the muscle and of muscle bundles, while the blood-vessels and lymphatics bring nourishment in the form of blood and lymph to the muscles and remove from the muscle the waste materials which are collected in blood and lymph. The nerves are branches from the central nervous system and pass from the nervous system to the muscles and control the movements of the latter.