A knowledge of the changes which man's diet has undergone from early times cannot but be of great value to the physician whether in enabling him to construct a rational dietary in health and disease or in helping him to interpret the many disorders which result from unsuitable food.
In respect of diet the mammalia fall into three classes - the carnivora, the herbivora, and the frugivora.
The carnivora subsist on an animal diet pure and simple, and this being highly concentrated, their digestive system is correspondingly small in relation to body weight.
The herbivora, of which the horse, the ox, and the rabbit may be cited as examples, subsist for the most part on bulky, uncon-centrated vegetable food, such as grasses, leaves, and the like, and have a correspondingly bulky digestive system. Animal food they avoid.
The frugivora, which include animals like the squirrel, the rat, and the monkey, consume vegetable food in its more concentrated forms, such as seeds and nuts. Being generally more intelligent than the herbivora, and gifted also with no inconsiderable prehensile powers, they are able to pick and choose their food more cleverly; and hence securing it in much more concentrated forms, they are provided with a much less bulky digestive system than the herbivora. Their intelligence and nimbleness moreover, often enable them to procure a certain amount of animal food - of all foods the most nutritious. Thus we find squirrels consuming eggs as well as nuts, and many of the monkeys, as also the great apes, supplementing their vegetable food by small birds, eggs, lizards, grubs, and the like.
Man, now essentially a mixed feeder, belongs by virtue of his descent, and as might be expected from his high mental and bodily development, to the frugivora.