“In the digestion of proteid food-stuffs by the combined action of gastric and pancreatic juice in the alimentary tract, a large proportion of the proteid is destined to undergo complete conversion into amino-acids; and, from these fragments, the body, by a process of synthesis, can construct its own peculiar type of proteid. This latter suggestion is worthy of a moment’s further consideration; as is well known, every species of animal has its own peculiar type of proteid, adapted to its particular needs. The proteids of one species directly injected into the blood of another species are incapable of serving as nutriment to the body, and frequently act as poison.... The availability or digestibility of food can be determined only by physiological experiment. By making a comparison, for a definite period of time, of the amount of the different food ingredients, and the amount that passes unchanged through the intestines, an estimate of its digestibility can be made.... In a general way it may be stated that with animal foods, such as meats, eggs, and milk, about 97 per cent. of the contained proteid is digested, and thereby rendered available to the body. With ordinary vegetables, on the other hand, as they are usually prepared for consumption, only about 85 per cent. of the proteid is made available. With a mixed diet, with a variable admixture of animal and vegetable foods, it is usually considered that about 92 per cent. of the proteid contained therein will undergo digestion.” At first sight, it would appear that this runs counter to the argument that has been advanced; but we must take into account the fact that Professor Chittenden is here speaking only of vegetable proteid, and has made no mention of _nuts_; and, as we have seen from the tables, nuts contain a far larger percentage of protein than meats. When we take into consideration the small disproportion in the percentage assimilated, and find that when meat is mixed with other articles of food, as it invariably is, the percentage of its availability is reduced to 92 per cent., while vegetable foods are proportionately raised to the same figure, we see that the apparent discrepancy practically vanishes to nothing. And when we further take into account the fact that an equal amount of proteid can be obtained from a far _less_ quantity of non-flesh food, we see that, from an equal bulk of food material, a far larger _proportionate_ percentage would be assimilated from the vegetable foods than from the animal.