150 FOOD INGESTION AND ENERGY TRANSFORMATIONS. 



INGESTION OF COFFEE. 



Although the earlier experimenters made but few observations on the 

 effect of drinking hot or cold water, we find a number of studies on the 

 effect of taking tea and coffee. Of special interest is the series of 

 experiments made by Bocker, 1 who concludes that the taking of coffee 

 decreases both extensively and intensively the respiratory processes. 

 Edward Smith 2 has a series of observations on drinking both tea and 

 coffee, and concludes that tea is a powerful respiratory stimulus, 

 coffee being but little less powerful. With the technique used by both 

 these investigators, it was not possible to study the fine differences 

 which in later times have been found to exist ; hence their results can 

 not be considered as conclusive. 



Speck 3 studied the effect of coffee-drinking in two experiments and 

 found a small but visible rise in the carbon-dioxide production and 

 oxygen consumption, indicating to his mind a distinct stimulus to the 

 digestive activities. Lehmann and Rohrer 4 found that the volatile 

 constituents of tea and coffee did not cause any noticeable changes in 

 the respiration frequency. A series of papers from the Russell Sage 

 Institute of Pathology has just appeared which includes a paper by 

 Means, Aub, and Du Bois, 5 reporting the results of a study in which 

 four normal subjects were given from 8 to 10 grains of caffein i. e., 

 8.6 milligrams per kilogram of body-weight. The authors state that 

 the basal metabolism was increased from 7.4 to 23.5 per cent, these 

 values representing average "peak" effects. Of special significance is 

 the fact that there was no material change in the pulse rate. 



STATISTICS OF EXPERIMENTS. 



Our own observations with coffee include two calorimeter experi- 

 ments made in Middletown and six respiration experiments in Boston. 

 The results are given in tables 80 to 87 and discussed in the accom- 

 panying text. They are also summarized in tables 67 and 68. (See 

 pages 135 and 136.) 



In all of the experiments the coffee was taken hot; in the two calo- 

 rimeter experiments a certain amount of sugar was also taken. The 

 general plan of both series of experiments was similar to that of the 

 water-drinking studies. The measurement of the gaseous metabolism 

 in the respiration experiments began 6 to 32 minutes after the drinking 

 of the coffee ; the total time between the taking of coffee and the end of 

 the last period ranged from 1 hour 31 minutes to 5 hours 29 minutes. 



The method of determining the total increment in the respiration 

 experiments was unlike that used in the chewing and water-drinking 

 studies in that the increase was found here by measuring plotted areas 



'Bocker, Beitriige zur Heilkunde, 1849, 1, p. 200. 



'Smith, Phil. Trans., 1859, 149, p. 715. 



'Speck, Physiologic des menschlichen Athmens, 1892, p. 42. 



4 Lehmann and Rohrer, Arch. f. Tlys;., 1902, 44, p. _'(:;. 



'Means, Aub, and Du Bois, Arch. Intern. M-<i. 1917, 19, p. 8:3:.'. 



