Carbon-Dioxide Elimination. 163 



erally speaking, about one-third of a gram of carbon dioxide per kilogram of 

 body-weight per hour is excreted by an individual during sleep. The amounts 

 in these experiments range from 0.278 gram in the case of the subject W. 0. A., 

 to 0.428 gram with the subject H. A. The average of all subjects is 0.354 

 gram. Expressing the results as cubic centimeters per minute, the experi- 

 ments show that, per kilogram of body-weight, the average excretion per minute 

 was 3.01 c. c. Variations are found ranging from 2.35 c. c. to 3.64 c. c. 



Per square meter of body-surface. As has been pointed out by Eubner and 

 others, the metabolism is not directly proportional to the body-weight but more 

 directly proportional to the body-surface, which bears a definite ratio to the 

 body-weight. 1 Consequently, in these experiments the calculations have also 

 been based on the carbon-dioxide excretion per square meter of body-surface 

 per hour, thus attempting to bring the experiments more into comparison than 

 by any other means. On the average, 11.6 grams of carbon dioxide are produced 

 per square meter of body-surface per hour during sleep, the variations ranging 

 from 9.9 grams with W. O. A. to 14 grams with H. A. Expressed in terms 

 of cubic centimeters per minute, the carbon-dioxide excretion per square meter 

 of body-surface varied with these subjects from 83.9 c. c. to 118.4 c. c, the 

 average excretion being 98.6 c. c. 



Comparison with Other Investigations on Carbon-Dioxide Elimination 



during Sleep. 



In comparing the results of these experiments with those of the earlier 

 writers, it is necessary to draw a sharp distinction between experiments made 

 with artificial mouthpieces or nosepieces and experiments made in which the 

 subject, breathing normally, is inclosed in a large chamber without being 

 obliged to give any particular attention to keeping the mouth tightly closed 

 around a mouthpiece, or the face held against a mask. 



It is quite inconceivable that even the most carefully trained subjects could 

 sleep and at the same time exercise all the precautions necessary when a mouth- 

 piece or mask is employed. Nevertheless, we find a number of experiments 

 in the literature in which the sleeping production of carbon dioxide was deter- 

 mined with a greater or less degree of accuracy. Employing his respiration 

 mask, Smith/ in 3 experiments, under conditions which the author describes 

 as " whilst awake but after lying down for some hours and with every approach 

 to sleep," exhaled carbon dioxide at the rate of 22.14, 22.92, and 23.70 grams, 

 respectively, per hour. In another experiment in which he reports " light 

 sleep, but probably not profound," he exhaled 19.08 grains per hour. In 

 another experiment, in which he reports that he was asleep, he gave off 19.44 

 grams per hour. 



3 'According to Meeh (loc. cit.), the body-surface is found by the formula S = 

 Vw X 12.312 in which S = body-surface in square centimeters and W = body- weight. 

 2 Smith, Philosophical Transactions, 1859, 149, p. 709; Sonden and Tigerstedt, 

 Skand. Archiv f. Physiol., 1895, 6, p. 104. 



