PROFESSOR VIRCHOW AND EVOLUTION. 637 



are the great agents of molecular disturbance. On the 

 inert molecules of seed and soil these waves impinge, dis- 

 turbing the atomic equilibrium, which there is an imme- 

 diate effort to restore. The effort, incessantly defeated 

 for the waves continue to pour in is incessantly renewed: 

 in the molecular struggle matter is gathered from the soil 

 and from the atmosphere, and built, in obedience to the 

 forces which guide the molecules, into the special form of 

 the tree. In a general way, therefore, the life of the tree 

 might be defined as an unceasing effort to restore a dis- 

 turbed equilibrium. In the building of crystals Nature 

 makes her first structural effort; we have here the earliest 

 groping of the so-called " vital force," and the manifes- 

 tations of this force in plants and animals, though, as 

 already stated, indefinitely more complex, are to be re- 

 garded of the same mechanical quality as those concerned 

 in the building of the crystal. 



Consider the cycle of operations by which the seed pro- 

 duces the plant, the plant the flower, the flower again the 

 seed, the causal line, returning witli the fidelity of a 

 planetary orbit to its original point of departure. Who or 

 what planned this molecular rhythm? We do not know 

 science fails even to inform us whether it was ever " plan- 

 ned " at all. Yonder butterfly has a spot of orange on its 

 wing; and if we look at a drawing made a century ago, of 

 one of the ancestors of that butterfly, we probably find the 

 selfsame spot upon the wing. For a century the molecules 

 have described their cycles. Butterflies have been begotten, 

 have been born, and have died; still we find the molecular 

 architecture unchanged. Who or what determined this 

 persistency of recurrence? We do not know; but we stand 

 within our intellectual range when we say that there is 

 probably nothing in that wing which may not yet find its 

 Newton to prove that the principles involved in its con- 

 struction are qualitatively the same as those brought into 

 play in the formation of the solar system. We may even 

 take a step further, and affirm that the brain of man the 

 organ of his reason without which he can neither think 

 nor feel, is also an assemblage of molecules, acting and 

 reacting according to law. Here, however, the methods 

 pursued in mechanical science come to an end; and if 

 asked to deduce from the physical interaction of the brain 

 molecules the least of the phenomena of sensation or 



