Upon such a diet the Eskimos lead an active and vigorous life. Their endurance and resistance to low temperature is shown in their excursions in company with white men in exploring the polar regions. Only the sturdiest white man, prepared by years of experience and training, can keep pace with the Eskimo in these dashes into the far North.

Considering the other extreme of the dietetic gamut, we may discuss the purely vegetarian diet. This consists of vegetables, cereals, legumes, fruits, and nuts. A purely vegetable diet as used by certain tribes in tropical regions and by certain religious votaries and faddists in subtropical regions. If properly selected, it is quite easy to arrange such a diet so that all of the needs of the body will be amply provided for. However, human experience seems to show that the purely vegetarian diet does not produce a people who possess the highest physical, intellectual, and moral qualities. The world's history does not show that a nation of vegetarians ever reached a high degree of civilization and maintained it for any appreciable length of time. That such is the case, however, must not be assumed to demonstrate that the reason for this is to be found in the diet. Perhaps that is only incidental. Vegetarian races have been tropical people. Their failure to reach and maintain the highest civilization may easily have been the result of the influence of the tropical climate.

The mixed diet consists of meat, eggs, milk, vegetables, fruit, cereals, nuts. In the mixed diet man eats everything that is edible. The people of the temperate zone have from time immemorial used mixed diet. This is probably due to necessity in early human history. They ate animals when they couldn't get vegetables and ate vegetables when they couldn't get animals. They, therefore, early learned to mix the diet, having both animal and vegetable foods in one menu. The cool, stimulating climate of Central and Northern Europe, Asia, and America stimulated primitive man to vigorous activity. He sought excitement. He found it in the chase. After the chase, assuming that to be successful, he barbecued the animal while the whole tribe gathered about and gorged to the limit. When the chase was not successful they usually had stores of cereals and nuts. In the warmer seasons of the year they ate freely of the fruits, berries, and succulent roots that grew on every hand. So we find the aggressive people who have accomplished so much, in the last two thousand years particularly, have used a mixed diet.

It must be evident that the flesh diet of the Eskimo, the vegetarian diet of the inhabitant of the tropics, and the mixed diet of middle latitudes have largely arisen from the necessities and exigencies of the life of primitive peoples in those respective regions. The world's work is accomplished by the people of the temperate zones, and these people use a mixed diet. That there is any causal relation between the diet and their work has not been proven. The relation is probably incidental and due rather to climatic than dietetic causes.

The ovo-lacto-vegetarian diet, last to be considered, is not the result of early human exigency, as were the other kinds of diet, but has been devised recently as a result of studies in the chemistry of nutrition; that eggs, milks, cereals, nuts, and legumes afford an ample source of nitrogenous foods has been amply demonstrated. Those who advocate this diet emphasize the fact that lean meat, being the muscle tissue of animals, killed in the midst of regular activities, naturally contains a considerable amount of effete and partially oxidized tissue waste on the way to excretion. Ingestion of such waste and semi-waste materials only embarrasses the nutrition of the man and places upon his excretory organs, particularly the kidneys, an extra and altogether unnecessary load of work. These materials would have been excreted presently by the kidneys of the beef creature or the mutton if his physiological activities had not been interrupted in the slaughter house. But having been interrupted, the process must be continued by the man who ingests these materials. Thus the man's kidneys become overworked. Furthermore, it is contended that even a moderate amount of eggs, milk, and legumes and nuts furnishes an ample supply of protein, and that the addition of lean meat to such a diet is so much in excess of the needs of the body, without any reference to the waste products above mentioned, that this excess of nitrogenous material tends to overwork the kidneys, therefore tends to accumulate within the body waste materials and fatigue products, which seriously interfere with all the activities of the body, both physical and intellectual.

In the light of recent researches in nutrition, these points seem to be well taken. An excess of nitrogenous material in nutrition does unquestionably embarrass nutritive processes, and this embarrassment leads surely to interference with the most efficient activity of the body. Whether the solution of the difficulty rests in the adoption of the ovo-lacto-vegetarian diet, or in some other hygienic change, has not been conclusively demonstrated.

Analysis of lean meat has demonstrated the presence of a substance called creatin. This is the substance which gives to lean meat its pleasing flavor, especially developed in the thoroughly cooked meats. Meat extract, beef extract, meat broths, and roast meat owe their pleasing flavor to creatin. Creatin seems to stimulate the appetite. The presence of a small amount of it, in soup or broth, stimulates the secretion of the gastric juice.

Mixed diet into which meat enters may be more condensed - that is, less bulky and more easily digested. Perhaps, therefore, the ovo-lacto-vegetarian diet has no advantages over very carefully chosen mixed diet, in which a moderate quantity of meat is introduced. The most recent researches in nutrition, in fact, tend to show that our mistakes in diet have not been so much in eating meat as the eating of excessive quantities of both meat and vegetables. When an individual eats too much, the error is almost invariably due to the fact that he eats too rapidly. If a person were to eat very slowly, thoroughly masticating every mouthful of food, chewing it until it is reduced to a creamy consistency, he would find after twenty or thirty minutes of such eating that his appetite had become completely satiated. He would also find that he had eaten a very much smaller amount than usual. The digestion of this thoroughly masticated food would proceed so rapidly and with such slight call upon the general system that the individual would be quite unconscious of his stomach and its activities. As the days and weeks go by, the individual adopting such a regime finds that he is maintaining his nutrition on a remarkably small amount of food, and that from this small amount of food he is deriving a remarkably large amount of energy.