Sir Oliver Lodge, famous physicist that he is, yet has a vein of mysticism and idealism in him which sometimes makes him recoil from the hard-and-fast interpretations of natural phenomena by physical science.  Like M. Bergson, he sees in life some tendency or impetus which arose in matter at a definite time and place, “and which has continued to interact with and incarnate itself in matter ever since.”

If a living body is a machine, then we behold a new kind of machine with new kinds of mechanical principles—­a machine that repairs itself, that reproduces itself, a clock that winds itself up, an engine that stokes itself, a gun that aims itself, a machine that divides and makes two, two unite and make four, a million or more unite and make a man or a tree—­a machine that is nine tenths water, a machine that feeds on other machines, a machine that grows stronger with use; in fact, a machine that does all sorts of unmechanical things and that no known combination of mechanical and chemical principles can reproduce—­a vital machine.  The idea of the vital as something different from and opposed to the mechanical must come in.  Something had to be added to the mechanical and chemical to make the vital.

Spencer explains in terms of physics why an ox is larger than the sheep, but he throws no light upon the subject of the individuality of these animals—­what it is that makes an ox an ox or a sheep a sheep.  These animals are built up out of the same elements by the same processes, and they may both have had the same stem form in remote biologic time.  If so, what made them diverge and develop into such totally different forms?  After the living body is once launched many, if not all, of its operations and economies can be explained on principles of mechanics and chemistry, but the something that avails itself of these principles and develops an ox in the one case and a sheep in the other—­what of that?

Spencer is forced into using the terms “amount of vital capital.”  How much more of it some men, some animals, some plants have than others!  What is it?  What did Spencer mean by it?  This capital augments from youth to manhood, and then after a short or long state of equilibrium slowly declines to the vanishing-point.

Again, what a man does depends upon what he is, and what he is depends upon what he does.  Structure determines function, and function reacts upon structure.  This interaction goes on throughout life; cause and effect interchange or play into each other’s hands.  The more power we spend within limits the more power we have.  This is another respect in which life is utterly unmechanical.  A machine does not grow stronger by use as our muscles do; it does not store up or conserve the energy it expends.  The gun is weaker by every ball it hurls; not so the baseball pitcher; he is made stronger up to the limit of his capacity for strength.