ADAPTATION. 237 



We have before found our conceptions of vital processes 

 made clearer by studying analogous social processes. In 

 societies there is a mutual dependence of functions, essen- 

 tially like that which exists in organisms; and there is also 

 an essentially like reaction of functions on structures. 

 From the laws of adaptive modification in societies, we may 

 therefore hope to get a clue to the laws of adaptive modifi- 

 cation in organisms. Let us suppose, then, that a 

 society has arrived at a state of equilibrium analogous to 

 that of a mature animal a state not like our own, in which 

 growth and structural development are rapidly going on, but 

 a state of settled balance among the functional powers of the 

 various classes and industrial bodies, and a consequent fixity 

 in the relative sizes of such classes and bodies. Further, 

 let us suppose that in a society thus balanced there occurs 

 something which throws an unusual demand on one industry 

 say an unusual demand for ships (which we will assume to 

 be built of iron) in consequence of a competing mercantile 

 nation having been prostrated by famine or pestilence. The 

 immediate result of this additional demand for iron ships is 

 the employment of more workmen, and the purchase of more 

 iron, by the ship-builders; and when, presently, the demand 

 continuing, the ship-builders find their premises and machi- 

 nery insufficient, they enlarge them. If the extra require- 

 ment persists, the high interest and high wages bring such 

 extra capital and labour into the business as are needed for 

 new ship-building establishments. But such extra capital 

 and labour do not come quickly; since, in a balanced com- 

 munity, not increasing in population and wealth, labour and 

 capital have to be drawn from other industries, where they 

 are already yielding the ordinary returns. Let us 

 now go a step further. Suppose that this iron-ship-building 

 industry, having enlarged as much as the available capital 

 and labour permit, is still unequal to the demand; what 

 limits its immediate further growth? The lack of iron. 

 By the hypothesis, the iron-producing industry, like all the 



