Even where a society that has developed into the highest form permittedby the characters of its units, begins to dwindle and decay, the progressivedissolution is still essentially of the same nature. Decline of numbers is,in such case, brought about partly by emigration; for a society having thefixed structure in which evolution ends, is one that will not yield and modifyunder pressure of population: so long as its structure is plastic it is stillevolving. Hence the surplus population is continually dispersed: the influencesbrought to bear on the citizens by other societies cause their detachment,and there is an increase of the uncombined motions of units instead of anincrease of combined motions. Gradually as the society becomes still lesscapable of changing into the form required for successful competition withmore plastic societies, the number of citizens who can live within its unyieldingframework becomes positively smaller. Hence it dwindles both through continuedemigration and through the diminished multiplication that follows innutrition.
And this further dwindling is similarly a decrease in the total quantityof combined motion and an increase in the quantity of uncombined motion --as we shall presently see when we come to deal with individual dissolution.
Considering, then, that social aggregates differ so much from aggregatesof other kinds, formed, as they are, of units held together loosely and indirectly,in such variable ways by such complex forces, the processes of dissolutionamong them conforms to the general law quite as clearly as could be expected. §179. When from these super-organic aggregates we descend to organicaggregates, the truth that Dissolution is a disintegration of matter causedby the reception of additional motion from without, becomes easily demonstrable.
We will look first at the transformation and afterwards at its cause.
Death, or that final equilibration which precedes dissolution, is thebringing to a close all those many conspicuous integrated motions that aroseduring evolution. The impulsions of the body from place to place first cease;presently the limbs cannot be stirred; later still the respiratory actionsstop; finally the heart becomes stationary and, with it, the circulatingfluids. That is, the transformation of molecular motion into the motion ofmasses, comes to an end. The process of decay involves an increase of insensiblemovements; since these are far greater in the gases generated than they arein the fluid-solid matters out of which the gases arise. Each of the complexchemical units composing an organic body, possesses a rhythmic motion inwhich its many component units jointly partake. When decomposition breaksup these complex molecules, and their constituents assume gaseous forms,there is, besides that increase of motion implied by diffusion, a resolutionof such motions as the complex molecules possessed, into motions of theirconstituent molecules. So that in organic dissolution we have, first, anend put to that transformation of the motions of units into the motions ofaggregates, which constitutes evolution, dynamically considered; and we haveafterwards, though in a subtler sense, a transformation of the motions ofaggregates into the motions of units. Still it is not thus shown that organicdissolution answers to the general definition of dissolution -- the absorptionof motion and concomitant disintegration of matter. The disintegration ofmatter is, indeed, conspicuous enough; but the absorption of motion is notconspicuous. True, the fact that motion has been absorbed may be inferredfrom the fact that particles previously integrated into a solid mass, occupyinga small space, have most of them moved away from one another and now occupya great space; for the motion implied by this expansion must have been obtainedfrom somewhere. But its source is not obvious. A little search, however,will bring us to its derivation.
At a temperature below the freezing point of water, decomposition of organicmatter does not take place. Dead bodies kept at this temperature are preventedfrom decomposing for an indefinitely long period: witness the frozen carcasesof mammoths (elephants of a species long ago extinct) that are found imbeddedin the ice at the mouths of Siberian rivers; and which, though they havebeen there for many thousands of years, have flesh so fresh that when atlength exposed it is devoured by wolves. What, now, is the meaning of suchexceptional preservations? A body kept below freezing point, is a body whichreceives very little heat by radiation or conduction; and the reception ofbut little heat is the reception of but little molecular motion. That isto say,in an environment which does not furnish it with molecular motionpassing a certain amount, an organic body does not undergo dissolution. Confirmatoryevidence is yielded by the variations in rate of dissolution which accompanyvariations of temperature. All know that in cool weather the organic substancesused in our households keep longer, as we say, than in hot weather. Equallycertain, if less familiar, is the fact that in tropical climates decay proceedsmuch more rapidly than in temperate climates. Thus, dispersion of the deadbody into gases is rapid in proportion as the molecular motion received fromwithout is great. The still-quicker decompositions produced by exposure toartificially-raised temperatures, afford further proofs: instance those whichoccur in cooking. The charred surfaces of parts much heated, show us thatthe molecular motion absorbed has served to dissipate in gaseous forms allthe elements but the carbon.
