VITALITY. 379 



molecular machinery through which the combining energy 

 acts may, in one case, weave the texture of a frog, while in 

 another it may weave the texture of a man. 



The matter of the animal body is that of inorganic 

 nature. There is no substance in the animal tissues which 

 is not primarily derived from the rocks, the water, and the 

 air. Are the forces of organic matter, then, different in 

 kind from those of inorganic matter? The philosophy of 

 the present day negatives the question. It is the compound- 

 ing, in the organic world, of forces belonging equally to the 

 inorganic, that constitutes the mystery and the miracle of 

 vitality. Every portion of every animal body may be 

 reduced to purely inorganic matter. A perfect reversal of 

 this process of reduction would carry us from the inorganic 

 to the organic; and such a reversal is at least conceivable. 

 The tendency, indeed, of modern science is to break down 

 the wall of partition between organic and inorganic, and to 

 reduce both to the operation of forces which are the same 

 in kind, but which are differently compounded. 



Consider the question of personal identity, in relation to 

 that of molecular form. Thirty-four years ago, Mayer of 

 Heilbronn, with that power of genius which breathes large 

 meanings into scanty facts, pointed out that the blood was 

 " the oil of the lamp of life," the combustion of which 

 sustains muscular action. The muscles are the machinery 

 by which the dynamic power of the blood is brought into 

 play. Thus the blood is consumed. But the whole body, 

 though more slowly than the blood, wastes also, so that 

 after a certain number of years it is entirely renewed. 

 How is the sense of personal identity maintained across 

 this flight of molecules? To man, as we know him, matter 

 is necessary to consciousness; but the matter of any period 

 may be all changed, while consciousness exhibits no solution 

 of continuity. Like changing sentinels, the oxygen, 

 hydrogen, and carbon that depart, seem to whisper their 

 secret to their comrades that arrive, and thus, while the 

 Non-ego shifts, the Ego remains the same. Constancy of 

 form in the grouping of the molecules, and not constancy 

 of the molecules themselves, is the correlative of this con- 

 stancy of perception. Life is a wave which in no two 

 consecutive moments of its existence is composed of the 

 same particles. 



Supposing, then the molecules of the human body, 



