CHAPTER VII. 

 METABOLISM, NUTRITION AND DIETETICS. 



WE return now to the products of digestion as they are 

 absorbed from the alimentary canal, and, still assuming a 

 typical diet containing proteids, carbo-hydrates and fats, we 

 have to ask, What is the fate of each of these classes of 

 proximate principles in the body ? what does each contribute 

 to the ensemble of vital activity ? It will be best, first of 

 all, to give to these questions what roughly qualitative 

 answer is possible, then to look at metabolism in its quanti- 

 tative relations, and lastly to focus our information upon 

 some of the practical problems of dietetics. 



i. Metabolism of Proteids. The two chief proteids of the 

 blood-plasma, serum-globulin and serum-albumin, must, as 

 has been already pointed out, be recruited from proteids 

 absorbed from the intestine and for the most part altered in 

 their passage through the epithelium which lines it. What 

 at bottom the reason and the mechanism of this alteration 

 are, we do not know ; but we do know that it is imperative 

 that peptone, and particularly albumose, should not appear in 

 quantity in the blood, for when injected they cause profound 

 changes in that liquid, one expression of which is the loss 

 of its power of coagulation, and are rapidly excreted by 

 the kidneys, or separated out into the lymph. It is not 

 definitely known whether the peptones formed in digestion 

 yield, under the influence of the epithelial cells, both the 

 chief proteids of the blood in the proportions in which they 

 xist in the plasma, or only one of them, which is afterwards- 



