210 LIFE AND DEATH. 



Before we define it a few preliminary explanations 

 are necessary. 



The most striking thing in living matter is its 

 growtJi. An animal, a vegetable, is something which 

 is first more or less minute, and which grows. Its 

 characteristic is to expand — from the spore, the seed, 

 the slip, the Q^g — it grows. 



Whether we are dealing with a cellular element, a 

 plastid, or a complex being, their condition is the 

 same in this respect. No doubt when the animal or 

 plant has reached a certain stage of development its 

 growth is stopped, and for a more or less lengthy 

 period it remains in the adult stage, in what seems to be 

 equilibrium. But even then there is no check in the 

 manufacture of living matter; there is only a com- 

 pensation between its production and its destruction. 



It is important to reduce to order the ideas on this 

 important subject, which at present are confused, 

 inconsistent, and contradictory. In biology grievous 

 confusion reiens. 



§ r. Effect of the Vital Activity. 

 Destruction or Growth? 



Distinction between the Living Substance and the 

 Reserve-stuff mingled with it — The physiology of 

 nutrition has given rise to a vast body of research 

 during the last half-century. Physiological schools, 

 masters and pupils, such as the school at Munich 

 under Voit and Pettenkofer, Pfluger's at Bonn, 

 Rubner's, and those of Zuntz and von Noorden at 

 Berlin, and a large number of zootechnical and "agri- 

 cultural laboratories through the whole world have for 



