CHAPTER XXXIV 



GROWTH 



" The living organism is so constituted that each disturbing influence stimu- 

 lates it to put in action a compensatory mechanism which will neutralise and 

 render innocuous the disturbing agency." FREDERICQ. 



GROWTH may be considered as an attempt of a system to get 

 into equilibrium with its environment. Generally, but not 

 invariably, increase in size is accompanied by changes in external 

 form and in internal structure. Development is, in most cases, 

 a necessary result of growth. This chapter will deal with increase 

 in size quite apart from any concomitant alterations in complexity. 



I. Nature of the Phenomenon. 



At first sight it seems easy to distinguish between a mere 

 accretion of material like crystal growth, snowball increase or 

 accumulation of interest on capital, and organic growth. A 

 more careful examination of the cause and resultant velocity of 

 growth shows that in both inorganic and organic worlds similar 

 principles are involved, and that similar factors operate towards 

 similar ends. 



A series of interesting and illuminating experiments emanating 

 from Leduc's laboratory are suggestive. If a little seed com- 

 pounded of copper sulphate and glucose be planted in a gelatine 

 (1-5 per cent.) gel, through which a little potassium ferrocyanide 

 has been dispersed, growth will take place. In the first place, by 

 the interaction of copper- and ferrocyanide-ions, a membrane of 

 copper ferrocyanide will be formed round the seed. This membrane 

 is semi-permeable, allowing free passage of water but preventing 

 the egress of the crystalloid ions. As a result, the seed, thus 

 gaining water by endosmosis, will swell up and, when the elastic 

 limit of the membrane has been reached, will burst. Immediately 

 this happens, a new membrane will form round the copper-glucose 



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