Oxygen Consumption. 179 



EXPERIMENTS ON OXYGEN CONSUMPTION. 

 Apparatus and Methods Used. 



The respiration apparatus formerly at Wesleyan University was so modified 

 as to include the determination of oxygen, and a description of the apparatus 

 was published in 1905. 1 The first experiments made with this apparatus in- 

 cluding the determinations of oxygen were published in 1907. 2 The results 

 there reported, together with the results of a series of experiments on fasting 

 man, 3 are included in the tables in the discussion beyond, and hence will not 

 receive special treatment here. As in the case of the experiments on carbon- 

 dioxide production and water vaporization, only those portions of the fasting 

 experiments that included the preliminary night and the first 24 hours are in- 

 cluded in the tables herewith. Usually the last meal was taken the evening 

 before at 6 or 7 o'clock; the observations began at 11 p. m. that night, and the 

 next morning at 7 a. m., the first fasting-day began and continued for 24 hours. 



As is to be expected in experiments in which so difficult a determination as 

 that of oxygen was attempted, a number of them gave results which were 

 plainly at variance with the normal variations accounted for in all cases by 

 the presence of a previously unsuspected leakage of air, hence they are not 

 included in the averages. This is particularly true of some of the experiments 

 of short duration. In experiments of 24 hours or more, we believe that the 

 determinations of oxygen with this apparatus are extremely accurate, and in 

 experiments of short duration where the subjects remained in the same bodily 

 activity at the beginning and end of each experiment, we believe that the 

 results are likewise accurate. But in a period, for example, between 11 p. m. 

 and 1 a. m., where at 11 p. m. the subject is sitting in a chair, clothed, and at 

 1 a. m. he is lying partially undressed, covered with bedding, there may be 

 such a marked difference in the temperature conditions inside of the chamber, 

 more particularly in the temperature gradient, that the determination of 

 oxygen may be seriously at fault. 4 



OXYGEN CONSUMPTION DURING SLEEP. 



As has been pointed out previously, the sleeping period from 1 a. m. to 7 a. m. 

 offers an exceptionally advantageous period for the study of the gas-exchange of 

 man inside a large respiration chamber. The bodily position of the subject at 

 7 a. m. is usually the same as that at 1 a. m. and the subject is usually in a pro- 

 found sleep. Results have been obtained during the night period with 15 sub- 

 jects, and with some of them a large number of experiments were made ; with 

 others but one. The results have been collected in table 71 herewith. For pur- 



1 Atwater and Benedict, Carnegie Institution of Washington Publication No. 42, 

 1905. 



2 Benedict and Milner, U. S. Dept. Agr., Office Expt. Stas. Bui. 175, 1907. 



3 Benedict, Carnegie Institution of Washington Publication No. 77, 1907. 



4 For a discussion of these sources of error, see Benedict and Milner, U. S. Dept. of 

 Agr., Office Expt. Stas. Bui. 175, pp. 24-32, 1907; and Benedict, Carnegie Institution 

 of Washington Publication No. 77, p. 448, 1907. 



