All change is _pro tanto_ death or _pro tanto_ birth. Change is the common substratum which underlies both life and death; life and death are not two distinct things absolutely antagonistic to one another; in the highest life there is still much death, and in the most complete death there is still not a little life. _La vie_, says Claud Bernard, {73a} _c’est la mort_: he might have added, and perhaps did, _et la mort ce n’est que la vie transformée_. Life and death are the extreme modes of something which is partly both and wholly neither; this something is common, ordinary change; solve any change and the mystery of life and death will be revealed; show why and how anything becomes ever anything other in any respect than what it is at any given moment, and there will be little secret left in any other change. One is not in its ultimate essence more miraculous that another; it may be more striking—a greater _congeries_ of shocks, it may be more credible or more incredible, but not more miraculous; all change is _quâ_ us absolutely incomprehensible and miraculous; the smallest change baffles the greatest intellect if its essence, as apart from its phenomena, be inquired into. But however this may be, all organic change is either a growth or a dissolution, or a combination of the two. Growth is the coming together of elements with _quasi_ similar characteristics. I understand it is believed to be the coming together of matter in certain states of motion with other matter in states so nearly similar that the rhythms of the one coalesce with and hence reinforce the rhythms pre-existing in the other—making, rather than marring and undoing them. Life and growth are an attuning, death and decay are an untuning; both involve a succession of greater or smaller attunings and untunings; organic life is “the diapason closing full in man”; it is the fulness of a tone that varies in pitch, quality, and in the harmonics to which it gives rise; it ranges through every degree of complexity from the endless combinations of life-and-death within life-and-death which we find in the mammalia, to the comparative simplicity of the amœba. Death, again, like life, ranges through every degree of complexity. All pleasant changes are recreative; they are _pro tanto_ births; all unpleasant changes are wearing, and, as such, _pro tanto_ deaths, but we can no more exhaust either wholly of the other, than we can exhaust all the air out of a receiver; pleasure and pain lurk within one another, as life in death, and death in life, or as rest and unrest in one another.