Page:Popular Science Monthly Volume 13.djvu/582

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cludes too much vitalism to suit our present purpose, which is to link the organic to the inorganic world.

We, therefore, cannot allow our scientific inquisitiveness to be arrested by the interposition of a mere name, or qualitas occulta. We do not wish to make known to others that contraction actually occurs in the living substance, for that is notorious. We wish to ascertain for ourselves how this contraction is effected—whether it is the work of entirely new forces exclusively appertaining to life, or whether it is the mechanical expression of molecular forces, with which we are already familiar in the domain of inorganic activities. Is it a specifically vital force which executes the contraction of motility? Or is it a molecular activity of a known kind which gives rise to vital motion?

This simple question may appear to some very unexciting; yet, upon its answer turns, nevertheless, the entire problem of life; for it is just at this point that the doom of vitalism has to be sealed. Vitalism or evolution: these two conceptions of Nature are incompatible. Vitalism means essentially the era of metaphysical agencies, the sway of extraneous powers coercing a resisting world of stubborn matter. Evolution means the era of inherent efficiency, the interaction of intrinsic powers ever elevating the constant realm of transient existences. It is of great importance, then, not to be deceived with regard to the exact manner in which this decisive vital act, the contraction of motility, is at all times being performed in Nature.

Fortunately, our monera give us plain information upon this point. It can be proved that it is chemical decomposition by which the liquefied and expanded material of the conical projection is caused to assume its former condition and place in space. The living substance contracts because it suffers decomposition, as can be directly witnessed. On the strength of this observation it would be quite legitimate to infer that it must have been chemical composition which also caused the reverse activity—which made a portion of the protoplasm start out from its globular limitation, and form a projection measuring in length in some cases more than three times the diameter of the main body. But we are not reduced to mere inference in this instance, so important to the understanding of vitality. By means of various accompanying appearances we can visibly ascertain that it is really a process of chemical composition which underlies the liquefaction and expansion of motility. This leading property of vitality is brought into actual play by the expansion of a certain substance in course of composition, and by the contraction of the same substance in course of decomposition, expansion and contraction being merely the physical concomitants of a definite chemical occurrence. This is shown on the one hand by the products of decomposition being separated and eliminated under our view, and on the other hand by the combining substances being brought together, and effecting their union during inspection. We have no occasion, then, to appeal to the intervention of any specific force in