“The organic substance of all organs and tissues, whether of animals or plants, is made up principally of proteid matter.... Proteid substances occupy, therefore, a peculiar position in the nutrition of man and of animals in general. They constitute a class of essential food-stuffs without which life is impossible. For tissue building, and for the renewal of tissues and organs, or their component cells, proteid or albuminous food-stuffs are an absolute requirement. The vital part of all tissue is proteid, and only proteid food can serve for its growth or renewal; hence, no matter how generous the supply of carbohydrates and fats, without some admixture of proteid food, the body will weaken and undergo ‘nitrogen starvation....’ It is thus quite clear that the true proteid foods are tissue builders in the broadest sense of the term, and it is equally evident that they are absolutely essential to life, since no other kind nor form of food-stuff can take their place in supplying the needs of the body. Every living cell, whether of heart, muscle, brain or nerve requires its due allowance of proteid material to maintain its physiological rhythm. No other food-stuff stands in such intimate relationship to the vital processes; and, so far as we know at present, any form of true proteid, whether animal or vegetable, will serve the purpose.”[14]
It will be seen from the above, therefore, that proteid is doubtless the most essential element in our diet; and a lack of proteid material in the food ensures more disastrous consequences to the organism than any other single deviation from a normal diet. Meat, as we have said, contains a large percentage of proteid, and, this being the case, it is evident that, if we are to discard it as an article of diet, we must replace it by other foods which contain an equal amount of proteid, or must eat a proportionate bulk of foods which contain proteid, in order to maintain that physiological equilibrium which ensures health.
The simplest, and in fact the _only_ way to settle this question, therefore, is to compare the chemical analyses of the various food-stuffs, and see if any non-flesh foods contain as much proteid as meat does. If they do, and if it can be shown, further, that their proteid is as easily assimilable and as nutritious as animal proteid, then the case will have been won—for the reason that there will no longer be any grounds for defending flesh-eating, upon the basis that that is the only article of diet capable of supplying the body with the requisite amount of proteid. I shall take these chemical analyses from the latest official bulletins—those issued under the supervision of the U. S. Department of Agriculture, and corrected up to 1908. The bulletin from which I quote these tables is entitled “The Chemical Composition of American Food Materials,” and is written jointly by Professors W. O. Atwater and A. P. Bryant. These authors first of all define what they mean by the “composition of food materials,” as follows:—