One of the first of the artificial foods for infants, was that ofLiebig. It was made by a master hand, so far at least as its chemistry was concerned. It contained the exact amounts of albumin, sugar, fat, and salts necessary for the nutrition of the child. But an extensive use proved that it failed in its object. The lesson which it teaches is only slowly gaining ground. That lesson is, that the animal organism requires something more for its maintenance than so much albumin, so much fat, and sugar, and mineral matter, It requires that these substances shall be of such kind, and in such form that they can be both digested, and assimilated. The examination of the food of the properly nourished individual, shows that he requires for instance, a given amount of proteid. Certain foods contain the proper amount of proteids. It is thereupon assumed that