CHAPTER V. 



NUTRITION. 



SEC. 1. THE STATISTICS OF NUTRITION. 



413. THE preceding chapter has 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 comparing 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 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 calcula- 

 tion 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 first datum we require 

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

 relative proportion of the various tissues is concerned. In the 

 human body the proportions by weight of the chief tissues, in 

 the fresh state, are probably somewhat as follows : 



Adult Man. Newborn Baby. 



Skeleton 15-9 p.c. 17*7 p.c. 



Muscles 41-8 22-9 



Thoracic viscera 1*7 3-0 



Abdominal viscera 7-2 11*5 



Fat 18-2 ) 20 . 



Skin 6-9 \ 



Brain 1*9 15-8 

 619 



