Probably the most striking evidence, certainly of an experimental nature, so far presented against the safety of a relatively low proteid diet for man is that based on the results of several studies made to ascertain the effect of a reduced proteid intake on so-called high proteid animals. Animal kind may be divided into three groups according to the nature of their food, viz., high proteid feeders, such as carnivorous animals in general, of which the dog is a good type; omnivorous or moderate proteid consumers, to which class man belongs; and low proteid consumers, such as herbivorous animals. Three series of experiments have been reported by independent workers on the effects of reducing the amount of proteid food in the diet of dogs. The results of these experiments were of such a character that it has come to be understood that animals of this type cannot exist for any great length of time on a low proteid diet. It is affirmed that in a relatively short period the animals reach such a state that they either die, or are in such poor condition that they must be fed a more liberal amount of proteid to maintain them alive. The explanation offered is that the low proteid diet results “in a loss of the power of absorption from the intestinal tract, caused apparently by a change in the condition of the epithelial cells, as well as by a diminished secretion of the digestive juices.” The argument based on this evidence is that while a high proteid animal feels at once, or almost immediately, the deleterious effect of a reduction in the amount of proteid food, an omnivorous animal may be more tardy in manifesting the injurious action, which, however, is sure to follow sooner or later from any material reduction of proteid below the customary standards. In other words, man as a moderate proteid consumer can endure for a time even large reductions in the amount of proteid food, but eventually there will be manifested some of the disastrous results obtained with dogs. Here, we have a somewhat serious indictment, one that merits careful consideration. To be sure, it may be objected that between dog and man there is a wide gulf, and that there is no justification for assuming that these two types of animal life have anything in common. Still, the experience of many years has taught the physiologist that much light can be thrown upon the processes of higher types of life by a study of what occurs in lower forms, and on the subject of nutrition any one of experience would hesitate to cast out of court the evidence gathered from observation of what occurs among the higher animals. It will be the part of wisdom, therefore, to scrutinize somewhat carefully the character of this evidence obtained from a study of the behavior of dogs toward a low proteid diet.