CHAPTER VI: SYSTEMS OF ORGANS.

§ 237a. The hypothesis of evolution implies a truth which was established independently of it—the truth that all animals, however unlike they finally become, begin their developments in like ways. The first structural changes, once passed through in common by divergent types, are repeated in the early changes undergone by every new individual of each type. Admitting some exceptions, chiefly among parasites, this is recognized as a general law.

This common method of development among individual organisms, we may expect to find paralleled by some common method among social organisms; and our expectation will be verified.

§ 238. In First Principles (§§ 149-152) and in the Principles of Biology (§§ 287-9) were described the primary organic differentiations which arise in correspondence with the primary contrast of conditions among the parts, as outer and inner. Neglecting earlier stages, let us pass to those which show us the resulting systems of organs in their simple forms.

The aggregated units composing the lowest cœlenterate animal, have become so arranged that there is an outer layer of them directly exposed to the surrounding medium with its inhabitants, and an inner layer lining the digestive cavity Edition: current; Page: [492] directly exposed only to the food. From units of the outer layer are formed those tentacles by which small creatures are caught, and those thread-cells, as they are called, whence are ejected minute weapons against invading larger creatures; while by units of the inner layer is poured out the solvent which prepares the food for that absorption afterwards effected by them, both for their own sustentation and for the sustentation of the rest. Here we have in its first stage the fundamental distinction which pervades the animal kingdom, between the external parts which deal with environing existences—earth, air, prey, enemies,—and the internal parts which utilize for the benefit of the entire body the nutritious substances which the external parts have secured. Among the higher Cœlenterata a complication occurs. In place of each single layer of units there is a double layer, and between the two double layers a space. This space, partially separate from the stomach in creatures of this type, becomes completely shut off in types above it. In these last the outer double layer forms the wall of the body; the inner double layer bounds the alimentary cavity; and the space between them, containing absorbed nutriment, is the so-called peri-visceral sac. Though the above-described two simple layers with their intervening protoplasm, are but analogous to the outer and inner systems of higher animals, these two double layers, with the intervening cavity, are homologous with the outer and inner systems of higher animals. For in the course of evolution the outer double layer gives rise to the skeleton, the nervomuscular system, the organs of sense, the protecting structures, etc.; while the inner double layer becomes the alimentary canal, with its numerous appended organs which almost monopolize the cavity of the body.

Early stages which are in principle analogous, occur in the evolution of social organisms. When from low tribes entirely undifferentiated, we pass to tribes next above them, we find classes of masters and slaves—masters who, as warriors Edition: current; Page: [493] carry on the offensive and defensive activities and thus especially stand in relations to environing agencies; and slaves who carry on inner activities for the general sustentation, primarily of their masters and secondarily of themselves. Of course this contrast is at first vague. Where the tribe subsists mainly on wild animals, its dominant men, being hunters as well as warriors, take a large share in procuring food; and such few captives as are made by war, become men who discharge the less skilled and more laborious parts of the process of sustentation. But along with establishment of the agricultural state, the differentiation grows more appreciable. Though members of the dominant class, superintending the labour of their slaves in the fields, sometimes join in it; yet the subject-class is habitually the one immediately in contact with the food-supply, and the dominant class, more remote from the food-supply, is becoming directive only, with respect to internal actions, while it is both executive and directive with respect to external actions, offensive and defensive. A society thus composed of two strata in contact, complicates by the rise of grades within each stratum. For small tribes the structure just described suffices; but where there are formed aggregates of tribes, necessarily having more-developed governmental and militant agencies, with accompanying more-developed industrial agencies supporting them, the higher and lower strata severally begin to differentiate internally. The superior class, besides minor distinctions which arise locally, originates everywhere a supplementary class of personal adherents who are mostly also warriors; while the inferior class begins to separate into bond and free. Various of the Malayo-Polynesian societies show us this stage. Among the East Africans, the Congo people, the Coast Negroes, the Inland Negroes, we find the same general sub-division—the king with his relatives, the class of chiefs, the common people, the slaves; of which the first two with their immediate dependents carry on the corporate Edition: current; Page: [494] actions of the society, and the second two those actions of a relatively-separate order which yield it all the necessaries of life.

§ 239. In both individual and social organisms, after the outer and inner systems have been marked off from one another, there begins to arise a third system, lying between the two and facilitating their co-operation. Mutual dependence of the primarily-contrasted parts, implies intermediation; and in proportion as they develop, the apparatus for exchanging products and influences must develop too. This we find it does.

In the low cœlenterate animal first described, consisting of inner and outer layers with intervening protoplasm, the nutritive matter which members of the inner layer have absorbed from prey caught by members of the outer layer, is transmitted almost directly to these members of the outer layer. Not so, however, in the superior type. Between the double-layered body-wall and the double-layered alimentary cavity, there is now a partially-separate peri-visceral sac; and this serves as a reservoir for the digested matters from which the surrounding tissues take up their shares of prepared food. Here we have the rudiment of a distributing system. Higher in the animal series, as in Mollusca, this peri-visceral sac, quite shut off, has ramifications running throughout the body, carrying nutriment to its chief organs; and in the central part of the sac is a contractile tube which, by its occasional pulses, causes irregular movements in the nutritive fluid. Further advances are shown by the lengthening and branching of this tube, until, dividing and sub-dividing, it becomes a set of blood-vessels, while its central part becomes a heart. As this change progresses, the nutriment taken up by the alimentary structures, is better distributed by these vascular structures to the outer and inner organs in proportion to their needs. Evidently this distributing system must arise between the two pre-existing Edition: current; Page: [495] systems; and it necessarily ramifies in proportion as the parts to which it carries materials become more remote, more numerous, and severally more complex.

The like happens in societies. The lowest types have no distributing systems—no roads or traders exist. The two original classes are in contact. Any slaves possessed by a member of the dominant class, stand in such direct relation to him that the transfer of products takes place without intervening persons; and each family being self-sufficing, there need no agents through whom to effect exchanges of products between families. Even after these two primary divisions become partially subdivided, we find that so long as the social aggregate is a congeries of tribes severally carrying on within themselves the needful productive activities, a distributing system is scarcely traceable: occasional assemblings for barter alone occur. But as fast as consolidation of such tribes makes possible the localization of industries, there begins to show itself an appliance for transferring commodities; consisting now of single hawkers, now of travelling companies of traders, and growing with the formation of roads into an organized system of wholesale and retail distribution which spreads everywhere.

§ 240. There are, then, parallelisms between these three great systems in the two kinds of organisms. Moreover, they arise in the social organism in the same order as in the individual organism; and for the same reasons.

A society lives by appropriating matters from the earth—the mineral matters used for buildings, fuel, etc., the vegetal matters raised on its surface for food and clothing, the animal matters elaborated from these with or without human regulation; and the lowest social stratum is the one through which such matters are taken up and delivered to agents who pass them into the general current of commodities: the higher part of this lowest stratum being that which, in workshops and factories, elaborates some of these materials Edition: current; Page: [496] before they go to consumers. Clearly, then, the classes engaged in manual occupations play the same part in the function of social sustentation, as is played by the components of the alimentary organs in the sustentation of a living body. No less certain is it that the entire class of men engaged in buying and selling commodities of all kinds, on large and small scales, and in sending them along gradually-formed channels to all districts, towns, and individuals, so enabling them to make good the waste caused by action, is, along with those channels, fulfilling an office essentially like that fulfilled in a living body by the vascular system; which, to every structure and every unit of it, brings a current of nutritive matters proportionate to its activity. And it is equally manifest that while in the living body, the brain, the organs of sense, and the limbs guided by them, distant in position from the alimentary surfaces, are fed through the tortuous channels of the vascular system; so the controlling parts of a society, most remote from the operative parts, have brought to them through courses of distribution often extremely indirect, the needful supplies of consumable articles.

That the order of evolution is necessarily the same in the two cases, is just as clear. In a creature which is both very small and very inactive, like a hydra, direct passage of nutriment from the inner layer to the outer layer by absorption suffices. But in proportion as the outer structures, becoming more active, expend more, simple absorption from adjacent tissues no longer meets the resulting waste; and in proportion as the mass becomes larger, and the parts which prepare nutriment consequently more remote from the parts which consume it, there arises the need for a means of transfer. Until the two original systems have been marked off from one another, this tertiary system has no function; and when the two original systems arise, they cannot develop far without corresponding development of this Edition: current; Page: [497] tertiary system. In the evolution of the social organism we see the like. Where there exist only a class of masters and a class of slaves, in direct contact, an appliance for transferring products has no place; but a larger society having classes exercising various regulative functions, and localities devoted to different industries, not only affords a place for a transferring system, but can grow and complicate only on condition that this transferring system makes proportionate advances.

And now, having observed the relations among these three great systems, we may trace out the evolution of each by itself.