224 Metabolism of Healthy Max. 



the average of some 30 experiment?. In table 91 the results from 12 days 

 entered into the average, i. e., 4 experiments of 3 days each. In these 4 experi- 

 ments, the average carbon-dioxide production from 1 a. m. to 7 a. m. was 22.5, 

 21.5, 22.4, and 23.1 grams, respectively. The heat production during the cor- 

 responding period was 62, 60, 61, and 59 calories, respectively. The calorific 

 equivalents of carbon dioxide in these 4 experiments were, then, 2.76, 2.79, 

 2.72, and 2.55 calories, respectively, the average being the low figure, 2.70 

 calories, reported in table 93. It is very much to be regretted that oxygen 

 determinations were not simultaneously made in the experiments with this 

 subject, but the experiments were all made prior to the completion of the method 

 for determining oxygen. 



The average carbon-dioxide calorific equivalent for the total 24 hours for all 

 subjects is 3.00 calories, and this may be taken as a normal value for subjects at 

 rest in the respiration calorimeter and subsisting on a mixed diet. 



Conclusions. From an examination of the results of the calorific equivalents 

 of oxygen and carbon dioxide, the difficulties of calculating the heat production 

 from measurements of either or both of these gaseous factors are apparent. 

 While the simultaneous measurement of all three factors, carbon dioxide, 

 oxygen, and heat, shows a uniform agreement between the energy of the material 

 katabolized from the body as computed from the chemical transformation and 

 the heat production during a 24-hour period, it is evident that using any one of 

 these factors by itself, it is practically impossible to compute the heat produc- 

 tion with an accuracy of less than 3 per cent. Of the two factors, by far the 

 more accurate for this purpose, i. e., showing the lesser variation from an aver- 

 age, is the oxygen consumption. Unfortunately, the determinations of the 

 oxygen consumption present the greatest difficulties difficulties that are, if 

 anything, not exceeded by the difficulties attendant upon the direct measure- 

 ment of the heat production. 



RELATION OF EXTERNAL MUSCULAR WORK TO CARBON-DIOXIDE ELIMINATION, 

 OXYGEN CONSUMPTION AND HEAT PRODUCTION. 



Very few forms of muscular work permit of an accurate measurement of the 

 calorific equivalent of the external muscular work performed. In experiments 

 in which the subject walks up an inclined plane one has to deal not simply Avith 

 the raising of the body to a given height, but likewise with the motion of for- 

 ward progression. When the subject climbs a ladder, the work performed can 

 be computed with considerable accuracy if the weight of the subject and the 

 height to which the body was moved are known. In order to measure the 

 external muscular work, such apparatus must be used as the brake ergometer, 

 the handles of which can be moved by the arms, the ergometer of Zuntz, 1 the 

 larger and more powerful machine devised by Johansson, 2 or a stationary 



1 Zuntz, Arch. f. Anat. u. Physiol., physiologische Ahtheilung, 1899, p. 372. 



2 Johansson, Skand. Archiv f. Physiol., 1901, 11; p. 273. 



