order to understand motility; that is, to understand it in the same manner as we understand other natural processes not belonging to vitality. We have here evidently only a display of specific chemistry. But, then, chemistry is specific all through down to H2O, CO2, and NH3, and who knows how much further?
Expansion and contraction are, as is well known, no uncommon physical concomitants of mere chemical activity, even without addition or subtraction of masses; and it is of fundamental importance clearly to comprehend that vital expansion and contraction are of the same chemical kind, being due to the intrinsic nature of the compound, not to the mere addition or subtraction of mass.
A part of the protoplasm of a moner expands. Chemical composition of a specific kind has taken place, and now it is the physical property of this peculiar compound to occupy more space than before; then the same part of the moner contracts in consequence of chemical decomposition. It is the physical property of the less complicated organic molecule to occupy so much less space. The mass of the added or separated material fills but a very small part of the entire space of expansion or contraction. The expansion as well as the contraction forms part of the specific nature of those different kinds of protoplasm. The organic substance of the moner, plus the separating molecule, is the expanded material. The organic substance of the moner, minus the separating molecule, is the contracted material. The activities of expansion and contraction are merely the physical expression of the gradual process of composition or decomposition occurring within the living substance; they are marks of the shifting of the special relation existing between the protoplasm and its medium during the transitional stages from one state of equilibrium to another.
The great truth which I wish to make quite evident is, that the specific nature of the acting substance constitutes the real power in motility, and not, as is usually believed, the addition of something from outside.
Vital processes will never become intelligible until it is clearly perceived that all vital efficacy resides in the living substance itself, forms an integral part of its specific nature. Many serious misconceptions are afloat with regard to the source of vital power. Science has as yet scarcely penetrated into the outermost precincts of the laboratory of life. The so-called vital dynamics of the present day are beggarly conceptions when measured against the actual wealth of vital manifestations. All we know is, that if so much pressure, so much heat, etc., will effect a new molecular equilibrium in a certain substance, that substance will return to the medium what it has received from it in reassuming its former state.
Will any one pretend to compute the value of the influences which the living substance in the course of ages has absorbed from its medium, in order to become what it at present is? Yet it is these assimi-
