50 FRAGMENTS OF SCIENCE. 



The matter of the animal body is that of inorgani 

 nature. There is no substance in the animal tissiN 

 which is not primarily derived from the rocks, 

 water, and the air. Are the forces of organic matt 

 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, 

 forces belonging equally to the inorganic, that coi 

 stitutes the mystery and the miracle of vitality. Eve 

 portion of every animal body may be reduced to purelj 

 inorganic matter. A perfect reversal of this pro< 

 of reduction would carry us from the inorganic to th< 

 organic ; and such a reversal is at least conceivabl 

 The tendency, indeed, of modern science is to breal 

 down the wall of partition between organic and in- 

 organic, and to reduce both to the operation of force 

 which are the same in kind, but which are differentl] 

 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 



