Page:Popular Science Monthly Volume 8.djvu/736

716 depends also on the organization, which enables the living thing to assimilate substances in large quantity and to dispose of an amount of nutrition in excess of the expenditure, just as a large capital, while it gives the means of undertaking great enterprises, at the same time yields increased profits.

The integration by an organism of substances homologous with its own has for its effect a segregation which increases the difference between the organism and the environment, and at the same time makes this difference stable. While the organism is being integrated, at the expense of the environment, by deriving from it special materials, each organ is being integrated at the expense of the organism, from which it derives, as from an environment, its special materials. Like the organism, each organ diverges more and more, by a gradual segregation, from the organs around about it. The organic units which constitute it attract other units with the same polarity, diffused throughout the fluids. This is not always the case, and homologous units do not always exist ready made in the nutrient fluid. More generally the organic units find in the fluids only the elements necessary for the production of homologous units, and segregation is perfected by a phenomenon of the nature of a genesis. Still in this case, as in the preceding, the result is a more perfect differentiation of the parts of the organism, an increase of heterogeneity, and augmentation of the distinction between the different parts, and ultimately the formation of a structure and of an actual organism. This result is called development.

Expressed in general terms, development is the transition from a state of incoherent homogeneity to a state of coherent and definite heterogeneity; from a state wherein the parts are all alike, or rather, where there are no distinct parts, to a state wherein there are parts clearly defined, with fixed forms and attributes. The bud of a plant consists of a hemispherical or subconical projection which, at its apex especially, is made up of a transparent mass of cells not yet organized into tissues. This mass grows owing to the rapid multiplication of the cells, lengthens, sends forth other similar projections having a like homogeneous structure; from this come leaves. As the branch develops, the cells, which at first were identical, assume different characters, till at last they lose all resemblance to one another. The same thing takes place in man. His arm is at first simply a little budding prominence on one side of the embryo, consisting of simple cells without any signs of arrangement. Soon there appear vessels, and later the cartilaginous parts from which are produced the bones, the gelatin-like bands which afterward are transformed into muscles, etc. In the individual we see the first phase of existence characterized by a state of homogeneity wherein nothing is distinct, and we follow step by step the gradations of its transition to a greater complexity, and to states characterized by increasing distinction of parts, as their