SEC. 3. THE STATISTICS OF N CJTRITIOX. 



The preceding sections have shewn us how wholly impossible 

 it is at present to master the metabolic phenomena of the body by 

 attempting to trace out forwards or backwards the several changes 

 undergone by the individual constituents of the food, the body or 

 the waste products. Another method is however open to us, the 

 statistical method. We may ascertain the total income and the 

 total expenditure of the body during a given period, and by com- 

 paring the two may be able to draw conclusions concerning the 

 changes which must have taken place in the body while the 

 income was being converted into the output. Many researches 

 have of late years been carried out by this method ; but valuable 

 as are the results which have been thereby gained, they must be 

 received with caution, since in this method of inquiry a small error 

 in the data may, in the process of calculation and inference, lead to 

 most wrong conclusions. The great use of such inquiries is to 

 suggest ideas, but the views to which they give rise need to be 

 verified in other ways before they can acquire real worth. 



Composition of the Animal Body. The rirst datum we require 

 is a knowledge of the composition of the body, as far as the rela- 

 tive proportion of the various tissues is concerned. In the human 

 body the proportions by weight of the chief tissues are probably 

 somewhat as follows : 



Adult man. Newborn baby. 



Skeleton 15'9 p. c. 177 p. c. 



Muscles 41-8 22'9 



Thoracic viscera 17 3'0 



Abdominal viscera 7'2 



Fat 18-2 



Skin 6'9 



Brain TO 



11-5 

 20'0 

 15-8 



