INGESTION OF COFFEE. 157 



DISCUSSION OF RESULTS OF COFFEE EXPERIMENTS. 



As the coffee was taken hot in both of the calorimeter experiments, 

 the same difficulties exist in making the proper correction for the 

 changes in body-temperature that were indicated in the water-drinking 

 experiments. With the subject A. H. M., in the calorimeter experi- 

 ment of April 19, 1907, a positive increase in the heat production 

 amounting to 11 per cent was noted. (See table 81.) Increments 

 as great, if not greater, were shown in the carbon-dioxide production 

 and oxygen consumption, thus confirming the fact that there was a 

 true increase in the metabolism. In this case a relatively large amount 

 of coffee, 1,011 grams, with 62 grams of sugar, was taken. That some 

 of the increase in the metabolism may properly be ascribed to the sugar 

 is clear from the data shown subsequently for the experiments in which 

 the effect of ingesting cane sugar was studied. 



In the experiment with A. W. W. on April 12, 1907, the amount of 

 coffee taken was much smaller, only 271 grams; in addition, 23 grams 

 of sugar were given. According to the data in table 80, there was an 

 actual lowering of the metabolism (3 per cent), with practically no 

 change in either the carbon-dioxide production or the oxygen consump- 

 tion. To a certain extent, then, this experiment is similar to the experi- 

 ments with hot water in which no material effect was observed on the 

 metabolism. In fact, neither of these two experiments can be taken 

 as giving positive evidence of an increase in the metabolism due to the 

 ingestion of coffee. 



The series of six respiration experiments with five subjects, all made 

 in March 1911, gave more convincing results. (See tables 82 to 87.) 

 In these experiments approximately 325 grams of coffee were taken 

 with a temperature, so far as known, of 50 to 60 C. The increments 

 averaged approximately 8 per cent, with a maximum of 13 per cent and 

 a minimum of 2 per cent. These positive increments in the metabolism 

 are distinctly at variance with the results of the calorimeter experi- 

 ment with A.W.W., in which a slight decrease appeared. But the 

 general trend is clear, and one may properly state that approximately 

 325 grams of coffee infusion at a temperature of about 60 C. will 

 produce an increment in the metabolism of 8 to 9 per cent. 



A careful analysis of the detailed data for these experiments shows 

 that in practically all instances the increment was by no means at an 

 end at the conclusion of the experiment; thus these figures probably 

 represent low rather than high values. For example, in the experiment 

 with J. J. C. on March 9, 1911, a basal metabolism of 222 c.c. of oxygen 

 consumed was recorded. Over 5 hours later, at the end of the experi- 

 ment, the oxygen consumption was 268 c.c. A similar long-continued 

 effect was noted with the same subject on March 21, 1911. It is thus 

 clear that the ingestion of coffee produces a positive increment in the 



