PREVIOUS INVESTIGATIONS. 19 



and the Pettenkofer method for determining the carbon dioxide. 

 Special emphasis was laid upon voluntary alteration of the type of 

 respiration which, as we know to-day, affects most the values for the 

 carbon-dioxide production. Nevertheless, taking into consideration 

 only his carbon-dioxide measurements, he finds interesting values 

 before and after food which should be noted here. Thus the carbon- 

 dioxide production per 15 minutes, when the respiration rate averaged 

 15 per minute, was during fasting 8.819 grams; after a rich meal it 

 increased to 9.960 grams, an increment of 1.141 grams, or approxi- 

 mately 12 per cent. An increase was also noted in the pulse rate from 

 65 beats per minute during fasting to 71 beats per minute after a rich 

 meal. In the average of the experiments with normal uncontrolled 

 respiration rate the value during hunger for the carbon-dioxide pro- 

 duction per 15 minutes was 4.866 grams and after a rich meal 6.613 

 grams, an increment of 1.747 grams or about 36 per cent. The pulse 

 rate increased from 52.4 to 61.3 per minute. 



In one interesting series of experiments, the effect of water-drinking 

 was studied. When the respiration rate was adjusted at 15 per minute 

 Berg found practically no increase in the carbon dioxide produced with 

 water as compared with the values found during thirst. A decrease of 

 3 beats per minute in the pulse rate was observed. With normal 

 uncontrolled respiration the carbon-dioxide production increased from 

 5.115 to 6.519 grams per 15 minutes after water, an increment of 1.404 

 grams or approximately 27 per cent; the pulse rate decreased 5.8 pulse 

 beats per minute. The author concludes that when experiments are 

 made hourly from 7 a. m. to midnight the energy of all the respiratory 

 functions increases after meal times. The maximum is observed 2 

 hours after the morning meal and 3 hours after the afternoon and even- 

 ing meals. These values pertain to the experiments in which the respi- 

 ration rate was controlled. With uncontrolled respiration the maxi- 

 mum values were noted immediately after each meal. It is clear that 

 the artificial regulation of respiration greatly affected the values found 

 by Berg. The results of his experiments are of interest only in sub- 

 stantiating practically all previous work to the effect that the incre- 

 ment due to the ingestion of food may be from 20 to 35 per cent. 



Speck, 1873. The possibility for change in the character of the 

 metabolism after the ingestion of food of varying chemical composition, 

 with consequent changes in the carbon-dioxide excretion not at all 

 commensurate with the true changes in energy transformation, led 

 Speck to make an extensive series of observations upon the respiratory 

 exchange in man, in which we find the first basic determinations of 

 oxygen consumption. By analyzing the expired air, which was col- 

 lected in a spirometer, Speck was able to determine the carbon-dioxide 

 increment and the oxygen deficit in the air passing through the lungs. 

 From these values he computed the carbon-dioxide production and the 



