The mechanism, and that is all. We see the workman and the tools, but the skill that guides the work and the power that performs it are as invisible as ever. I fear that not every listener took the significance of those pregnant words in the passage I quoted from John Bell,--“thinking to discover its properties in its form.” We have discovered the working bee in this great hive of organization. We have detected the cell in the very act of forming itself from a nucleus, of transforming itself into various tissues, of selecting the elements of various secretions. But why one cell becomes nerve and another muscle, why one selects bile and another fat, we can no more pretend to tell, than why one grape sucks out of the soil the generous juice which princes hoard in their cellars, and another the wine which it takes three men to drink,--one to pour it down, another to swallow it, and a third to hold him while it is going down. Certain analogies between this selecting power and the phenomena of endosmosis in the elective affinities of chemistry we can find, but the problem of force remains here, as everywhere, unsolved and insolvable. Do we gain anything by attempting to get rid of the idea of a special vital force because we find certain mutually convertible relations between forces in the body and out of it? I think not, any more than we should gain by getting rid of the idea and expression Magnetism because of its correlation with electricity. We may concede the unity of all forms of force, but we cannot overlook the fixed differences of its manifestations according to the conditions under which it acts. It is a mistake, however, to think the mystery is greater in an organized body than in any other. We see a stone fall or a crystal form, and there is nothing stranger left to wonder at, for we have seen the Infinite in action. Just so far as we can recognize the ordinary modes of operation of the common forces of nature,--gravity, cohesion, elasticity, transudation, chemical action, and the rest,--we see the so-called vital acts in the light of a larger range of known facts and familiar analogies. Matteuecci's well-remembered lectures contain many and striking examples of the working of physical forces in physiological processes. Wherever rigid experiment carries us, we are safe in following this lead; but the moment we begin to theorize beyond our strict observation, we are in danger of falling into those mechanical follies which true science has long outgrown. Recognizing the fact, then, that we have learned nothing but the machinery of life, and are no nearer to its essence, what is it that we have gained by this great discovery of the cell formation and function?