INGESTION OF PROTEIN DIETS. 265 



INGESTION OF PREDOMINATINGLY PROTEIN DIETS. 



No single nutrient, when ingested, produces so great an effect upon 

 the metabolism as protein does. In fact, the earlier observations, par- 

 ticularly those made by Rubner and Magnus-Levy with dogs and man, 

 appeared to show that protein was the only nutrient which measurably 

 increased the metabolism. At the time of beginning our study on the 

 effect of food upon the metabolism, the varieties of pure protein avail- 

 able were relatively limited. Accordingly the largest number of experi- 

 ments were made with beefsteak, for though this food material was not 

 a pure protein, it was palatable and easily obtained. Furthermore, as 

 the beefsteak given the subject was freed from all visible fat, it was 

 assumed that the amount of fat ingested would play but a small part 

 in the metabolism. In a number of the beefsteak experiments small 

 amounts of bread or potato chips were also taken. In some of the 

 observations approximately pure protein materials were used, these 

 being gluten, plasmon, and in the later experiments in Boston, glidine. 

 The gluten and plasmon were both taken with skim milk. 



In the experiments with relatively pure protein and in a large pro- 

 portion of the beefsteak experiments the observations were made with 

 the calorimeter. While these experiments do not by any means fulfill 

 the demands of the technique at the present time, they do represent 

 the first attempt with man to determine by direct calorimetry the 

 influence upon the metabolism of the ingestion of protein; conse- 

 quently they are discussed in some detail. One defect in the plan of 

 experimenting for all of the Middletown calorimeter experiments and 

 for the majority of the Boston calorimeter experiments is the fact that 

 the basal values and the values after the ingestion of protein were not 

 determined on the same day. 



Although the experiments with gluten and skim milk and plasmon 

 and skim milk were made in 1906, while those with beefsteak were not 

 begun until 1907, it seems desirable to consider first the data with the 

 single food materials, especially as so large a number of observations 

 were made with beefsteak. 



BEEFSTEAK. 

 MIDDLETOWN CALORIMETER EXPERIMENTS. 



The four Middletown experiments, which were made with but two 

 subjects, are best discussed according to the amounts of food ingested, 

 as they were planned for comparison purposes. In the first pair of 

 experiments, those with A. H. M. on April 5, 1907, and A. W. W. on 

 April 6, 1907, a large amount of beefsteak was taken, the measurements 

 of the metabolism beginning about an hour after the subject had 

 finished eating. In the second set of observations with the same sub- 



