GROWTH. 147 



To obtain materials for growth; to avoid injuries which 

 interfere with growth; and to escape those enemies which 

 bring growth to a sudden end; implies in the organism the 

 means of fitting its movements to meet numerous external 

 co-existences and sequences — implies such various structural 

 arrangements as shall make possible these variously-adapted 

 actions. It cannot be questioned that, everything else re- 

 maining constant, a more complex animal, capable of adjust- 

 ing its conduct to a greater number of surrounding con- 

 tingencies, will be the better able to secure food and evade 

 damage, and so to increase bulk. And evidently, without 

 any qualification, we may say that a large animal, living under 

 such complex conditions of existence as everywhere obtain, 

 is not possible without comparatively high organization. 



While, then, this relation is traversed and obscured by 

 sundry other relations, it cannot but exist. Deductively we 

 see that it must be modified, as inductively we saw that it is 

 modified, by the circumstances amid which each kind of or- 

 ganism is placed, but that it is always a factor in determining 

 the result. 



§45. That growth is, cceteris paribus, dependent on the sup- 

 ply of assimilable matter, is a proposition so continually illus- 

 trated by special experience, as well as so obvious from general 

 experience, that it would scarcely need stating, were it not re- 

 quisite to notice the qualifications with which it must be taken. 



The materials which each organism requires for building 

 itself up, are not of one kind but of several kinds. As a 

 vehicle for transferring matter through their structures, all 

 organisms require water as well as solid constituents; and 

 however abundant the solid constituents there can be no 

 growth in the absence of water. Among the solids supplied, 

 there must be a proportion ranging within certain limits. A 

 plant round which carbonic acid, water, and ammonia exist 

 in the right quantities, may yet be arrested in its gro^vth by 

 a deficiency of potassium. The total absence of lime from its 



