100 FOOD INGESTION AND ENERGY TRANSFORMATIONS. 



carbon dioxide with varying respiratory quotients, and the possibility 

 of an over- ventilation of the lungs accompanied by an excessive carbon- 

 dioxide production. 



EXPERIMENTS WITH H. L. H. 



The most extensive series of experiments was obtained with Mr. 

 H. L. Higgins, who was long connected with the experimental work of 

 the Nutrition Laboratory. The first experiment with this subject was 

 on May 23, 1910, and the last on June 2, 1915; although not made at 

 regular intervals, the observations were reasonably well distributed 

 over this period of about five years. Confining our discussion first to 

 the carbon-dioxide values and considering the influence upon them of 

 the time of day and their variation in the consecutive periods, we find 

 that the carbon-dioxide production per minute shows considerable 

 variation from hour to hour in the individual experiments. (See 

 table 37.) Differences as large as 20 c.c. or more are occasionally 

 noted, this corresponding to an approximate variation of 10 per cent. 

 Thus in the experiment of September 24, 1911, there was a difference 

 between the first and second periods of 26 c.c. and between the first 

 and fourth periods of 31 c.c., or nearly 15 per cent of the average value 

 for the day, while the values for January 13, 1912, show a difference 

 between the second and third periods of 30 c.c., again about 15 per 

 cent of the average for the day. The average values for the consecu- 

 tive periods are remarkably constant. The highest is that for the first 

 period, 203 c.c., drawn from 10 periods; the lowest is that for the fifth 

 period, 195 c.c., drawn from 21 periods. Although the average value 

 for the fifth period is lower than that for the first, we do not find here, 

 as with some of the experiments made with the 8-hour method, any 

 tendency towards a falling off or material alteration of the values as 

 the day progresses. 



The greatest mean variation, 11.3 c.c., occurs in the first period, this 

 being slightly more than 5 per cent of the average value for this period. 

 The mean variation of the averages for all the periods is but 7.8 c.c., 

 an agreement that indicates uniform experimental conditions and ac- 

 curacy in technique. 



From the general picture of the carbon-dioxide production of this 

 subject during the period of five years, which is obtained from the 

 averages in the extreme right-hand column, we find that while there 

 are individual variations there is no general tendency toward a material 

 alteration in the metabolism; this is further confirmed by the small 

 average mean variation. We may therefore infer that the carbon- 

 dioxide production of this subject did not vary to any extent in the 

 course of the five years of experimenting. The average carbon-dioxide 

 production for H. L. H., as shown by the determinations made during 

 this period, may be considered as 198 c.c. per minute. 



