Discussion of Results. 105 



CONSTANCY IN METABOLISM AS REPORTED BY EARLIER WRITERS. 



From an examination of the earlier literature it may be seen that in the 

 researches of Andral and Gavarret, 1 and in the simultaneously published re- 

 searches of Scharling 2 there are a number of experiments, particularly in the 

 first case, which may reasonably be considered as duplicates. Thus, Andral 

 and Gavarret find that the same subject exhaled in 1 hour amounts of carbon 

 dioxide represented by from 10.4 to 11.2 grams of carbon. This was the sixth 

 experiment with this subject, the average of all the experiments being 10.7 

 grams. With a second subject, the amounts of carbon per hour varied from 

 8.5 grams to 8.8 grams in 4 experiments. Scharling's duplicate results are 

 not quite so evident, but on examining table 1 on page 492, and table 2 on 

 page 493 of his original article, it is seen that the amount of carbon per hour 

 was reasonably constant with the same conditions of muscular activity and of 

 ingestion of food. 



Assuming that the carbon dioxide is a true index of the total metabolism, 

 these researches in themselves would indicate that the metabolism was con- 

 stant with the same individual, but we now know that the carbon dioxide is but 

 imperfectly indicative of the total metabolism as the amount of carbon dioxide 

 may vary considerably, depending upon the character of the diet. Since, 

 however, the heat production in general varies more nearly as the oxygen 

 intake, a much more satisfactory index is the accurate measurement of the 

 oxygen consumption and fortunately,, as a result of the work of Zuntz and 

 his co-workers, we have much material on this point, particularly with regard 

 to the total metabolism of men at rest, breathing through special appliances, 

 although in experiments of but a few minutes' duration. The experiments 

 prior to the researches of Speck and Zuntz throw very little light upon the 

 accurate determination of oxygen with man in experiments continuing two or 

 more hours. The heat measurements are also lacking in a large majority of 

 experiments. It appears, therefore, that the experiments at Wesleyan Uni- 

 versity furnish data regarding the largest number of individuals in which 

 all these three factors of metabolism, carbon-dioxide excretion, oxygen con- 

 sumption, and heat production were studied, and for this reason it is especially 

 advantageous to note the constancy or lack of constancy in the results obtained. 



DUPLICATION IN SERIES HERE PUBLISHED. 



Accordingly, the results of certain of these experiments have been included 

 in a large table (table 45) so as to show comparable averages of carbon-dioxide 

 output, oxygen intake, and heat production per hour with any particular indi- 

 vidual. Data for 14 different subjects are presented and a total of 48 experi- 

 ments have been included in the enumeration, which, so far as numbers go, 

 makes reasonably sound such deductions as may be drawn from the comparisons. 



1 Andral and Gavarret, Ann. de Chim. et de Phys., 1843, ser. 3, 8, p. 129. 



2 Scharling, Ann. de Chim. et de Phys., 1843, ser. 3, 8, p. 478; also in the Ann. der 

 Chem. und Pharm., 1843, 45, p. 214. 



