212 LIFE AND DEATH. 



principles of the organism, reduced to a lower degree 

 of complexity. 



Destruction of Reserve-stuff. But now the disagree- 

 ment begins. What are these decomposed, destroyed 

 principles ? Do they belong to the cellular reserve- 

 stuff or to the living matter properly so called ? 

 There is no doubt that most of them belong to the 

 reserve-stuff. For example, this is especially true of 

 glycogen, which is consumed in muscular contraction 

 just as coal is consumed in the furnace of the loco- 

 motive ; and glycogen is a reserve-stuff of muscle. 

 These reserve-stuffs destroyed in the functional 

 activity can be built up again only during repose. 



But it is not yet certain whether the living 

 matter itself, the active protoplasm, the muscular 

 protoplasm, takes part in this destruction, whether it 

 provides it with elements. Experiments have proved 

 contradictory. Experimenters have isolated the nitro- 

 genous wastes (urea) after muscular labour, and they 

 have compared them with the wastes of the period of 

 repose. These nitrogenous wastes bear witness to the 

 destruction of albuminoid substances, and the latter 

 are the constituent principles of living matter. If 

 under conditions of sufficient alimentation the mus- 

 cular functional activity involves more nitrogenous 

 waste, i.e., a greater destruction of albuminoids, it 

 might be supposed that the living material properly 

 so called has been used up and destroyed for its 

 own purposes. (And here again there might be a 

 reserve-stuff of albuminoids, distinct from the living 

 protoplasm itself, and more or less incorporated 

 with it.) 



But experiment so far has not given decisive results. 

 The latest experimental researches, such as those of 



