104 Metabolism of Healthy Max. 



tion chamber has been made with subjects sitting upright, while practically 

 all the experiments in which special breathing appliances were used, especially 

 those giving the most scientifically accurate results, have been made with sub- 

 jects lying down. 



For the purpose of this report, namely, the study of the normal metabolism 

 of man, the earlier results, i. e., with special nose or mouth appliance, are not 

 satisfactory from the very fact that the subjects were lying down awake, 

 whereas, with man, the period of lying awake is ordinarily not very long. It 

 must be admitted that the confinement within a respiration chamber is not 

 wholly normal, but the number of hours spent per day in sitting awake is 

 much greater normally than that in lying awake, and hence the values obtained 

 with subjects sitting upright in the respiration chambers do throw light upon 

 the metabolism of man when not doing extraneous muscular work, such as 

 walking, or muscular work in the course of a trade or profession. 



Duplication of Results in Individual Metabolism. 



In publishing the results of the experiments here reported, our primary 

 object is to present a mass of material that can be used for drawing deductions 

 regarding the normal gross metabolism of man, but, before discussing this 

 subject, it is important to see whether there is constancy with the same indi- 

 vidual under like conditions of muscular activity and diet. As a result of a 

 number of preliminary observations it has been found that changes in muscular 

 activity, body condition, diet, etc., may produce noticeable alterations in the 

 total metabolism, and hence, these experiments have been made with as many 

 individuals as possible and under like conditions. Frequently duplicate or 

 triplicate experiments were made with the same subject. The statistical details 

 have been given in the preceding section and it is now proposed, in the first 

 place, to demonstrate to what extent one can rely upon duplicate experiments 

 with the same individual. 



The physiological processes are so complex that it might be questioned 

 whether duplication of results can be obtained, even with the same individual, 

 for when it is considered that metabolism includes the operation of a large 

 number of forces, with a most complex chemical constitution involved in each 

 transformation, it should not be at all surprising to find a lack of constancy 

 from day to day. If the results in experiments with one subject vary con- 

 siderably from time to time, and precautions have been taken to secure uniform 

 conditions, obviously, the average of the various results obtained can not be 

 taken as representing the normal metabolism of that individual. If, on the 

 contrary, the metabolism remains constant, the average for this individual 

 can be taken as typical and his metabolism can, with perfect propriety, be 

 compared with that of other subjects under similar conditions. 



