176 INTELLIGENT BEHAVIOUR 
the wider, freer, and more varied life of the higher animals 
the plastic survives and the stereotyped succumbs. 
Imperfect as is our present knowledge of the manner 
in which the nervous connections implied in psychological 
associations are established, there can be no question that 
they are acquired in the course of individual life; they are 
modifications of nervous structure due to a special mode of 
use under the conditions of experience. Here, then, in the 
case of the nervous system, as in that of the bodily organs 
before mentioned, two factors determine the limits of efficiency 
—heredity and use. And these two, again, co-operate in such 
a way that we may say, either that due use—here represented 
by adequate experience—is the essential condition of the 
effective development of the hereditary potentialities, or that 
heredity serves to condition their effective development 
through use and experience. And just as the heart and lungs 
must inherit the power of standing abnormal strain if the 
animal is to avoid elimination in times of unwonted exertion, 
so must the nervous system inherit some reserve power of 
dealing effectively with unwonted circumstances by intelligent 
accommodation, if the animal is not to fall a victim to such 
circumstances. In other words, at times of heightened com- 
petition those animals which can draw on a reserve fund of 
intelligent accommodation will survive, while the stupid 
blunderers will be eliminated. We may term this reserve 
fund of intelligent accommodation, this inherited ability to 
meet specially difficult circumstances as they arise, inate 
capacity. From the nature of the case it must be indefinite, 
for it must carry with it the ability to meet unforeseen 
combinations of the environing forces by new combinations 
of the results of experience. Its distinguishing mark is 
plasticity, in contradistinction to the stereotyped fixity of 
typical instinct. And accompanying its evolution there is 
probably, as we have seen, a dissolution of its antithesis, 
instinct. Thus may we account for the fact that man, with 
his great store of innate capacity, has so small a number of 
stereotyped instincts. 
