CHAPTER Y. 



i 



NUTRITION. 



SEC. 1 THE STATISTICS OF NUTRITION. 



519. 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 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 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 : 



