THE METABOLISM OF THE BODY. 



In the widest sense the term metaboitsm may be conven- 

 iently applied to all the numerous changes of a chemical kind, 

 resulting from the activity of the protoplasm of any tissue or 

 organ. In a more restricted meaning it is confined to changes 

 undergone by the food from the time it enters till it leaves the 

 body, in so far as these are not the result of obvious mechanical 

 causes. The sense in. which it is employed in the present 

 chapter will be plain from the context^ though usually we shall 

 be concerned with those changes effected in the as yet compara- 

 tively unprepared products of digestion, by which they are ele- 

 vated to a higher rank and brought some steps nearer to the 

 final goal toward which they have been tending from the first. 

 As yet our attempts to trace out these steps have been little 

 better than the fruitless efforts of a lost traveler to find a road, 

 the general direction of which he knows, but the ways by which 

 it is reached only the subject of plausible conjecture. We 

 shall therefore not discuss the subject at length from this point 

 of view. 



THE METABOIilSM OF THE I.IVER. 



This organ has two well-recognized functions : 1. The for- 

 mation of bile. 2. The formation of glycogen. We have 

 already considered the first. 



Glycogen may be obtained from the liver of mammals as a 

 whitish amorphous powder, having the chemical composition of . 

 starch, and has in fact been termed animal starch. 



By appropriate treatment it may be converted into sugar by 

 a process of hydration (CeHioOs + H3O = CeHiaOi). 



The principal facts as to the storage of glycogen in the liver 

 may be briefly stated thus : 



1. Glycogen has been found in the liver of a large number 



