86 



THE CRITERIA OF LIVINGNESS 



bodies by provoking an immediate and violent reactional 

 response to the introduction of any substance v^hich might 

 change it.'' 



(c) Persistence in Spite of Change. 



In the ordinary chemical changes in the inorganic domain, 

 as in the weathering of rocks, one substance changes into 

 another. Iron becomes rust. So is it also in the living 

 body, but there we encounter a new and characteristic fea- 

 ture — continual restitution or recuperation. The reactions 

 are not self-destructive. Repair counteracts waste ceaselessly. 

 There is a continual balancing of accounts so that debts are 

 more or less effectively avoided. Without metaphor, the 

 specific organisation is continuously repaired so that the 

 specific activity continues, and if organisms — after they 

 once got grip — had been content to remain relatively simple 

 they need never have died — a natural death. 



We regard this characteristic as fundamental, — the capac- 

 ity of retaining integrity in spite of ceaseless specific change, 

 — one may almost say through change. For the energy lib- 

 erated in katabolism is used to promote compensating anabo- 

 lism. The more it changes, the more it remains the same 

 thing; the most intensely living animals have the most per- 

 sistent integrity of form. In any case, an organism was 

 not worthy of the name until it showed, for a time at least, 

 not merely activity, but persistent activity — a power of bal- 

 ancing accounts. Like a clock the organism is always run- 

 ning down and always needing to be wound up ; but unlike 

 a clock it can wind itself up, if it gets food and rest. In 

 green plants, as every one knows, there is usually a quite 

 unnecessary amount of winding up — with the interesting 

 far-oif result that animals, utilising already manufactured 



