METABOLISM. 



By E. A. SCHAFER. 







CONTENTS : Introductory, p. 868 Balance of Nutrition, p. 871 Composition of 

 Foodstuffs, p. 872 Heat Value of Foodstuffs, p. 874 Necessary Amount of 

 Proteid, p. 875 Special Constituents of Diet, and their Effect on Metabolism, 

 p. 878 Gelatin, p. 878 Carbohydrates, p. 880 Fats, p. 881 Inorganic Sub- 

 stances, p. 882 Metabolism in Inanition, p. 887 With purely Proteid Diet, 

 p. 891 Relative Metabolic Activity of Tissues, p. 895 Nitrogenous Meta- 

 bolism, p. 896 Influence of the Liver on Proteid Metabolism, p. 900 Influence 

 of Muscular Activity on Proteid Metabolism, p. 911 Metabolism of Carbo- 

 hydrates, p. 916 Glycogen formation, p. 919 Phloridzin Diabetes, p. 920 

 Glycogenesis, p. 922 Puncture Diabetes, p. 926 Action of Pancreas on 

 Carbohydrate Metabolism, p. 927 Metabolism of Fat, p. 930 Source and 

 Formation of Fat, p. 931 Action of Liver on Metabolism of Fat, p. 935. 



Introductory. The word " metabolism " has come into use in this 

 country as the equivalent of the German word StoffwecJisel, which 

 strictly means " exchange of material." The subject which it denotes 

 embraces all that is known or conjectured regarding the changes which 

 occur within the body in the materials of the food, or foodstuff's, and 

 in the materials which compose the tissues and organs of the body 

 itself, or bodystuffs. Generally, however, the digestive changes in the 

 food are excluded from the scope of the expression. There is 110 special 

 reason, other than that of convenience of description, why this should be 

 the case, for the digestive changes in the food must, like all other 

 chemical changes occurring within the body, influence the general con- 

 ditions of the economy. The usual course will, however, be followed 

 in this article, and I shall confine what I have to say to the changes that 

 occur after the food is absorbed, in so far as they have not been already 

 treated of in the articles in this work dealing with the chemistry of the 

 urine and with the chemical processes of respiration and heat production, 

 both of which .subjects constitute essential parts of the whole subject 

 of metabolism. 



The metabolic changes which are undergone by the tissues must bo 

 of two kinds, which are opposite in nature. 1 For, on the one hand, the 

 complex molecules which constitute living tissue or bioplasm, 2 are built 



1 Hering, " Vorgiinge der lebenden Materie," Prag, 1888. A translation, by Miss F. A. 

 Welbv, of this extremely important and interesting article will be found in Brain, London, 

 1807, vol. xx. p. 232. 



2 I use the word bioplasm as a synonym for living substance, rather than protoplasm, 

 because the latter word has come to have a definite histological rather than a physiological 

 signification ; and, on the one hand, is used to include portions of cell substance which, for 

 aught we know, may not be actually living matter, whilst, on the other hand, it does not 

 include the living substance of the cell nucleus, which would be included in the expression 

 "bioplasm." 



