he became in some degree its master. As cultivation improved, it was found that only a small proportion of the population was required to raise crops, fruits and cattle, and the remainder were released to use their brains and brawn in other channels.

First villages sprang up, then towns and cities. Industrialism was initiated, the arts had their disciples, and finally that complex division of labor and of occupations which marks the social progress known as modern civilization was gradually evolved. All this wonderful progress was due to the cultivator of the soil and the breeder and rearer of domesticated animals termed the farmer. The farmer who tills the soil and raises flocks and herds, and the fisherman who reaps the harvest of the seas, are still the most necessary members of the community, for by the labor of the farmer and fisherman, especially the farmer, sufficient food is produced to maintain a vast population whose energies are released for specialized work. Consequently, up to a certain point diet has played the principal part in the evolution of man.

Relation of Climate to Diet.—But although agriculture, man's own invention, has varied and amplified the food supply, it is necessary to emphasize the natural features which affect diet. A direct relation exists between climate and the consumption of food. In cold climates, exercise and cold sharpen the appetite, and therefore more food is consumed. On the other hand, in a warm climate leading to a state of inactivity, there is less inclination to eat.

Not only is there a correspondence between the amount of food ingested and the inclination for taking it, but probably, from the exercise of instinct supplemented by experience, the nature of the food selected, in different climes, is found to vary, and to constitute that which is most in conformity with what is needed. Moreover, the various climates produce in a large degree the kind of food best suited to keep the inhabitants in health. Vegetables which produce carbohydrates will not grow in very cold climates, and, even if they could be grown, they could not be consumed in sufficient quantities to yield the necessary amount of heat. The dwellers in the arctic regions consume prodigious amounts of heat-generating material, fatty matter procured from the bodies of seals and whales which abound in that part of the world. Conversely, the inhabitants of the torrid zone subsist chiefly on vegetable products highly charged with carbohydrate material in place of fat. The vegetables and fruits which grow in the tropics are exactly adapted to the bodily needs of the inhabitants. The succulent fruits and vegetables upon which the natives of very hot countries prefer to feed, contain little carbon, whereas,

the oil and blubber which enter largely into the diet of those who live in the extreme north, contain a very large proportion of carbon.

A temperate climate lends itself more to an omnivorous diet, something between the two extremes of far north and far south.

Custom in such climates has led to the selection of a mixed diet, which furnishes the combination of the two heat-producing principles. The diet should be made to conform to the principle of adaptability to the particular requirement existing. It should be pointed out that in discussing the question of the evolution of man's diet, the dwellers in the temperate climates are almost invariably referred to. Most of what has been said does not apply at all, or only partly, to the inhabitants of the arctic regions and of the tropics.

In order to give emphasis to these statements, it will be of interest to quote from various authors describing the kind of food consumed by the inhabitants of different parts of the globe.

Lubbock (17) reports that "the Eskimos are mainly an animal-feeding people, and their food consists of reindeer, musk-ox, walrus, seals, birds and salmon. They will, however, eat any kind of animal food, and are fond of fat and marrow."

Simmond (18) says: "The choicest dish of the Greenlanders is the flesh of the reindeer. But as these animals have now become extremely scarce, they are indebted to the sea for their permanent sustenanceseals, fish and sea fowl. The heads and fins of the seal are preserved under the grass in summer, and in winter a whole seal is frequently buried under the snow. The flesh, half frozen, half putrid, in which state the Greenlanders term it mikiak, is eaten with the keenest appetite."

Mackenzie (19) says: "The diet of the Icelanders consists almost solely of animal food, of which fish, either fresh or dried, forms by far the largest proportion. During the summer they have milk or butter in considerable abundance; but of bread and every other vegetable food, there is the utmost scarcity. As an effect of these circumstances, cutaneous diseases are exceedingly frequent. Scurvy and leprosy are common in the island. Scurvy is observed to occur with the greatest frequency at those periods when there has been a deficiency of food among the inhabitants or when the snow and frost of the winter succeed immediately to a wet autumnal season. For its cure, a vegetable diet is employed, in as far as the circumstances of the Icelanders will allow of such means."

Wrangell (20) writes that "the food of the Jakuts of northern Siberia consists of sour cow's milk and mare's milk, and of beef and horseflesh. They boil their meat, but never roast or bake it, and bread is unknown

among them. Fat is their greatest delicacy.

In general, they regard

quantity more than quality in their food. They grate the inner bark of the larch, or sometimes of the fir, and mix it with fish, a little meal and milk, or by preference with fat, and make it into a sort of broth. They prepare from cow's milk what is called the Jakut butter. It is more like a kind of cheese or curd, and has a sourish taste; it is not very rich and is a good article of food eaten alone.”

F. B. Head (21) says: "The Indians of whom I heard the most were those who inhabit the vast unknown plains of the Pampas and who pass their lives on horseback. In spite of the climate, which is burning hot in summer and freezing in winter, they have neither bread, fruit nor vegetables, but subsist entirely on the flesh of their mares." Head said of himself that when he had been riding across the Pampas for three or four months and had lived on beef and water, he found himself in a condition which he could only describe by saying that he felt no exertion could kill him (22). Referring to the Gauchos of the Pampas he stated: "These people live entirely on roast beef, with a little salt, scarcely ever tasting farinaceous or other vegetable food, and their sole beverage is mate, or Paraguay tea, without sugar."

It is said of the Otaheite Islanders (23), "Their common diet is made up of at least nine-tenths of vegetable food."

In China any kind of food is eaten, while in Japan a multiplicity of food is found. In all parts of the Far East, rice is the staple of diet. According to Johnston (24), the Abyssinians eat the flesh of animals raw when they desire to enjoy themselves particularly.

Simmond (18) says that "the principal diet of the Kaffir is milk, which he eats rather than drinks, in a sour and curdled state. One good meal a day taken in the evening, consisting of the curdled milk and a little millet, is all that he requires, and with this he is strong, vigorous and robust."

It would seem from a perusal of the observations of the travelers. quoted above with regard to the diet of people in various climes, that no hard and fast rule can be laid down as to the kind of food to be eaten. Still in a broad way the statement may be reiterated that instinct and experience are generally the best guides as to the form of food best. adapted to the individual. Animal food is mainly indicated for cold climates, vegetable food for the tropics, and a mixed diet for the temperFood adapted to the inhabitants is, as a rule, that which can be procured in the neighborhood.

ate zone.

Seasonal Variation of Diet.-The change of seasons exerts some influence on the diet of man. Before agriculture, domestication of animals and cooking came to pass, the influence thus exerted was greater. This is shown by the diet of the primitive races of the present day, which is almost entirely regulated by the seasonal occurrence of vegetable and animal foods. Among civilized communities independence of and indifference to the seasons have been brought about by the elaborate and effective means which have been devised for preserving, storing, and to a less extent for artificially producing food.

Among modern communities an article of food is never out of season. Food of every description, which can be raised and brought to maturity in one or other part of the world, is, owing to the facilities for rapid transit on sea and land, and more especially to the perfection of the methods of preservation and storage, conveyed at any season of the year to the very doors of those who can afford to pay for it. All kinds of food, even highly perishable vegetable foods, are available at all seasons. Although this system has its advantages, unfortunately it lends itself to abuse. Speculators have been quick to seize upon the opportunities afforded for making money at the expense of the pockets and health of the community. Also when food material is preserved and stored for a long period, the continued freezing deteriorates the quality of the food and this system becomes a menace to health. Animal food preserved for a protracted period is not nearly so nourishing as fresh meat, and when preserved too long may be absolutely injurious. However, preservation of food when properly employed is a great boon to the race.

CHANGES IN BODILY STRUCTURE AND FUNCTION DUE TO EVOLUTION

MODIFICATIONS DUE TO VARIATION OF DIET

It is self-evident that changes in function and structure have accompanied or followed evolutionary dietetic progress. The faculty of digesting both animal and vegetable food has varied in the periods of man's evolutionary progress. So far as animal food is concerned, this faculty waxed and waned in proportion to the quantity consumed during the various diet. epochs, and was most in evidence when man depended chiefly upon animal food for his subsistence.

The capacity of men of those times to digest immense quantities of food material may be surmised from the fact that certain peoples of the

present era consume and digest enormous amounts of animal food. Of these the Eskimos, who perhaps may be regarded as being in the same stage of evolution as the men of the early hunting period, are the most conspicuous examples. It appears certain that the capacity of the Eskimo to digest animal food greatly exceeds that of the ordinary civilized individual; and it seems even more certain that the capacity in this direction of the man of the early hunting period was still greater.

Our ancestors of the simian stage possessed the power to digest coarse vegetable foods to an extent unknown to the present day inhabitants of the earth. Like the apes, to which they were very nearly akin in those days, their jaws and teeth were formed to masticate cellulose, and their digestive organs were of a character to deal effectively with it and the other constituents of the vegetables, which they were compelled to eat in order to live. Also, and this is an important point, since cookery has done away with the necessity for the prolonged mastication of vegetable food which was naturally accompanied by excitation of the salivary glands, it may be taken for granted that the salivary glands of primitive man possessed more amylolytic power than those of neo-man, who, owing to the softness of his food, masticates little. The development of agriculture and the advance of cookery have had the effect of greatly diminishing the consumption of raw vegetables; consequently the power of digesting this form of food has waned until, at the present time, very few uncultivated vegetable foods are eaten raw, with the exception of a few of the cultivated varieties of fruits. Further modifications in the digestive organs were brought about by an increase in the supply of sugar and starch. The cultivation of sugar canes and other sugar-producing plants. increased man's previous supply of sugar immensely, and the ability to extract sugar from the cane, and especially from the beet root, augmented it beyond conception. Long ago cookery and agriculture added to the quantity of starchy material available for food, and in recent years cookery has added to the supply of soluble saccharids. As always, in utilizing this additional food supply, man's digestive organs have become more tolerant of starch and sugar.

Natural selection has played the great part in all these adaptations. Those who could not adapt themselves to this kind of food were weeded out in infancy, and a type of the human species has been, and is being evolved, whose digestive organs are able to cope with very large amounts of starch and sugar. The great personal adaptability of man to the various kinds of food must be taken into consideration. Of the animals the frugivorous mixed feeding type is the most adaptable to diet. Man has