INGESTION OF PROTEIN DIETS. 305 



The series of respiration experiments which are summarized in table 

 215 were made subsequent to most of the calorimeter experiments 

 included in table 230 and were designed to throw more light upon 

 the quantitative relationships. Varying amounts of beefsteak were 

 taken in these experiments, although in none was so large an amount 

 eaten as in the first two calorimeter experiments given in table 230. 

 The heat production in the periods subsequent to the taking of the food 

 invariably exceeded the basal value. Usually the experiments were 

 not continued sufficiently long to include the total effect of the food, 

 so that the basal value would again be reached; consequently the 

 increases recorded in the last two columns of table 215 frequently 

 represent incomplete increments. Most of the experiments did not 

 extend over a period longer than 6 hours, although in one case the 

 observations were continued over a period of nearly 12 hours. The 

 irregularity in the effect upon different individuals of the ingestion of 

 the same amount of nitrogen is strikingly shown in the percentage 

 increase above the basal value, these figures being given in the last 

 column of the table. While theoretically we should expect to find con- 

 tinually decreasing values for these percentages, as the experiments 

 are arranged in the table in the order of decreasing amounts of beef- 

 steak eaten, this is not actually the case. 



Making due allowance for the fact that the time over which the 

 experiments were continued varies somewhat, it is still clear that there 

 is no uniform relationship between the amount of nitrogen ingested 

 and the actual increase above the basal metabolism. Whether such 

 a relationship could have been established if the experiments had been 

 continued until the effect of food had completely ceased would appear, 

 from the data obtained, extremely improbable. Experiments of this 

 length are very tiresome for both subject and observer; nevertheless 

 such experiments should ultimately be made. For the present, there- 

 fore, we can only reiterate the deductions made from the results of 

 the calorimeter experiments to the effect that while the ingestion of 

 protein in almost any amount invariably produces an increase over 

 the basal metabolism which may be 25 per cent for several hours 

 and for short periods may rise to 45 per cent (see tables 198 to 229), 

 no definite mathematical relationship between the amount of protein 

 ingested and the increment in the total metabolism can be noted from 

 these values. It is probable that in any study of these results it 

 should be remembered that these subjects were unlike in body-weight 

 and in active mass of protoplasmic tissue. 



