50 FKAGMENTS OF SCIENCE. 



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 ques- 

 tion. It is the compounding, in the organic world, of 

 forces belonging equally to the inorganic, that con- 

 stitutes 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 in- 

 organic, 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 per- 

 sonal identity maintained across this flight of mole- 

 cules ? 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 



