PART 3. DISCUSSION OF RESULTS. 



When we consider the chemical complexity of man's organism, the con- 

 siderable differences in size, weight, and temperament, and the marked changes 

 in diet and physical activity in the course of his daily life, it is difficult to 

 imairine him as having - a normal metabolism to which all metabolism measure- 

 ments can be referred. No two people may be said to be alike even in physical 

 appearance, and it is reasonable to suppose that, when all the factors of life 

 are taken into consideration, this lack of similarity will be even more apparent. 

 Different people would, therefore, be expected, a priori, to show marked differ- 

 ences in metabolism, and yet the collection of statistics regarding the metabolic 

 functions of individuals approximating uniformity in size, weight, physical 

 activity, and general development will give results of distinct value and interest. 

 It is obvious that for general use the results obtained from a careful study 

 of one or two individuals can have but little bearing on the study of the 

 normal requirements of man in general, and hence it is important to make 

 studies of a large number of individuals and eliminate the personal equation 

 in order to draw satisfactory deductions with regard to the normal metabolism 

 of man. It is, furthermore, important to group individuals according to 

 size, weight, or physical development, and note if the averages drawn from the 

 results indicate merely the " might of average figures " or if they truly represent 

 the average metabolism of individuals of a stated physical characteristic. 



Comparison of Methods. 



In order to study a large number of individuals in this way and with the 

 proper degree of care, special apparatus is necessary. The urine can be readily 

 collected and analyzed, and the products which are excreted determined, with- 

 out particular difficulty; consequently, we find records of the protein metab- 

 olism of a large number of individuals. The study of the total metabolism, 

 however, requires much more elaborate apparatus, a need which has been 

 supplied by the respiration apparatus, and the experiments in respiration thus 

 far made can be placed in two important groups according to the two different 

 methods employed. By one method the metabolism of a large number of indi- 

 viduals is studied simultaneously; by the other, the individuals are studied 

 separately, and thus any differences due to the personal equation may be 

 carefully noted. 



Group method. The first method is that which has been employed with 

 such signal success by Sonden and Tigerstedt. 1 By this method of experi- 



1 Sonden and Tigerstedt, Skand. Archiv f. Physiol., 1895, 6, p. 1. 



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