Either in himself, or in his descendants continuing to live under these conditions,enforced repetition must at length bring about a state in which this modeof directing the energies will be no more repugnant than the other modespreviously natural to the race. Hence the limit towards which emotional modificationperpetually tends, is a combination of desire that correspond to the variousorders of activity which the circumstances of life call for. In acquiredhabits, and in the moral differences of races and nations that are producedby habits maintained through successive generations, we have illustrationsof this progressive adaptation, which can cease only with the establishmentof equilibrium between constitution and conditions. §175. Each society displays the process of equilibration in the continuousadjustment of its population to its means of subsistence. A tribe of menliving on wild animals and fruits, is manifestly, like every tribe of inferiorcreatures, always oscillating from side to side of that average number whichthe locality can support. Though, by artificial production unceasingly improved,a superior race continually alters the limit which external conditions putto population; yet there is ever a checking of population at the temporarylimit reached. It is true that where the limit is being rapidly changed,as among ourselves, there is no actual stoppage: there is only a rhythmicalvariation in the rate of increase. But in noting the causes of this rhythmicalvariation -- in watching how, during periods of abundance, the proportionof marriages increases, and how it decreases during periods of scarcity,it will be seen that the expansive force produces unusual advance wheneverthe repressive force diminishes, and vice versa; and thus there is as neara balancing of the two as the changing conditions permit.
The internal actions constituting social functions, exemplify the generalprinciple no less clearly. Supply and demand are continually being adjustedthroughout all industrial processes; and this equilibration is interpretablein the same way as preceding ones. The production and distribution of a commodityimply a certain aggregate of forces causing special kinds and amounts ofmotion. The price of this commodity, is the measure of a certain other aggregateof forces expended in other kinds and amounts of motion by the labourer whopurchases it. And the variations of price represent a rhythmical balancingof these forces. Every rise or fall in the value of a particular security,implies a conflict of forces in which some, becoming temporarily predominant,cause a movement that is. presently arrested, or equilibrated, by the increasedopposing forces; and amid these daily and hourly oscillations lies a moreslowly-varying medium, into which the value ever tends to settle, and wouldsettle but for the constant addition of new influences. As in the individualorganism so in the social organism, functional equilibrations generate structuralequilibrations. When on the workers in any trade there comes an increaseddemand, and when in return for the increased supply they receive an amountof other commodities larger than before -- when, consequently, the resistancesovercome by them in sustaining life are less than the resistances overcomeby other workers; there results a flow of other workers into this trade.
This flow continues until the extra demand is met, and the wages so far fallthat the total resistance overcome in obtaining a livelihood, is as greatin this newly-adopted occupation as in the occupations whence it drew recruits.
The occurrence of motion along lines of least resistance, was before shownto necessitate the growth of population in those places where the labourrequired for self-maintenance is the smallest; and here we further see thatthose engaged in any such advantageous locality, must multiply till therearises an approximate balance between its population and that of others availableby the same citizens.