Oxygen Consumption. 181 



oxygen consumption on this basis varies from 8.9 grams with W. 0. A. to 13.1 

 grams with H. A., the average for all subjects being 10.5 grams. Converting 

 these values to cubic centimeters per square meter of body-surface per minute, 

 we have 101 c. c. as the minimum and 153 c. c. as the maximum, the average 

 for all subjects being 123 c. c. of oxygen absorbed per square meter of body- 

 surface per minute. 



The variations in the amounts of carbon dioxide excreted by different indi- 

 viduals are in part explained in that the quantities of carbon dioxide excreted 

 are influenced in large part by the nature of the materials burned during the 

 experiment. While there may be large differences in the carbon-dioxide produc- 

 tion with the same individual and with different individuals when compared on 

 the basis of per kilo and per square meter, on the other hand it is commonly 

 supposed that the oxygen absorption remains relatively constant, and with like 

 body activity the same individual would absorb the same amount of oxygen, 

 and different individuals would absorb relatively the same amount of oxygen 

 per kilogram of body-weight. In these experiments the variations in the oxygen 

 consumption are so noticeable that they can be explained only on the basis that 

 there were marked differences in the actual katabolism with different indi- 

 viduals. Furthermore, an examination of data not presented in this table 

 shows that with the same individual there may be during the sleeping period 

 likewise noticeable differences in the oxygen consumption. This statement is, 

 indeed, somewhat at variance with a statement made in the earlier part of this 

 report in which the uniformity of results with the same individual has been 

 emphasized (see page 106). Where variations in the oxygen consumption do 

 occur, the only explanation that can be made is that there were actual differ- 

 ences in the katabolism, which may be affected by factors such as restlessness 

 during sleep or, indeed, the influence of the preceding muscular exertion. (See 

 discussion of this point on page 183.) It is also of importance to note here 

 that an examination of the results in table 90 showed that in general the respi- 

 ratory quotients remained relatively constant throughout the night experiments. 

 Consequently, the variations in the carbon-dioxide production noted in these 

 experiments must likewise be taken as being affected not so much by changes 

 in the kind of material burned but by changes in the total amount of material 

 burned, a change induced by a variation of the total katabolism. 



Comparison with Other Investigations on Oxygen Consumption during Sleep. 



Experiments on oxygen consumption of man during sleep are confined to a 

 few investigators. The criticism has been raised above that with the ordinary 

 mouthpiece or nosepiece the experiments made during sleep must of necessity 

 be considered as of a somewhat doubtful value, since with muscular relaxation 

 there would be a liability to a leak around the mouth or nose. With the method 

 of studying the respiratory exchange employed by Speck it would be impossible 

 to make experiments on subjects lying asleep, although he emphasizes the im- 

 portance of making experiments during sleep if possible. 



