VIRCHOW AND EVOLUTION. 289 



others they will appear as proofs of genius on the part of those "who 

 enunciated them. There are men, and by no means the minority, who, 

 however wealthy in regard to facts, can never rise into the region of 

 principles ; and they are sometimes intolerant of those who can. They 

 are formed to plod meritoriously on the lower levels of thought, un- 

 possessed of the pinions necessary to reach the heights. They cannot 

 realize the mental act — the act of inspiration it might well be called — 

 by which a man of genius, after long pondering and proving, reaches a 

 theoretic conception which unravels and illuminates the tangle of cen- 

 turies of observation and experiment. There are minds, it may be said 

 in passing, who at the present moment stand in this relation to Mr. 

 Darwin. For my part, I should be inclined to ascribe to penetration 

 rather than to presumption the notion of a contagmm animatum. He 

 who invented the term ought, I think, to be held in esteem ; for he 

 had before him the quantity of fact and the measure of analogy that 

 would justify a man of genius in taking a step so bold. " Neverthe- 

 less," saj's Prof. Virchow, " no one was able throughout a long time to 

 discover these living germs of disease. The sixteenth century did not 

 find them, nor did the seventeenth, nor the eighteenth." But it may 

 be urged, in reply to this, that the theoretic conjecture often legiti- 

 mately comes first. It is the forecast of genius which anticipates the 

 fact and constitutes a spur toward its discovery. If instead of being 

 a spur the theoretic guess rendered men content with imperfect knowl- 

 edge, it would be a thing to be deprecated. But in modern investiga- 

 tion this is distinctly not the case ; Darwin's theory, for example, like 

 the undulatory theory, has been a motive power and not an anodyne. 

 " At last," says Prof. Virchow, " in the nineteenth century we have 

 begun little by little really to find contagia animata. So much the 

 more honor is due to those who, three centuries in advance, so put 

 together the facts and analogies of contagious disease as to divine its 

 root and character. Prof. Virchow seems to deprecate the "obstinacy" 

 with which this notion of a contaghim vivum emerged. Here I should 

 not be inclined to follow him ; because I do not know, nor does he tell 

 me, how much the discovery of facts in the nineteenth century is 

 indebted to the stimulus derived from the theoretic discussions of pre- 

 ceding centuries. The genesis of scientific ideas is a subject of pro- 

 found interest and importance. He would be but a poor philosopher 

 who would sever modern chemistry from the eflForts of the alchemists, 

 who would detach modern atomic doctrines from the speculations of 

 Lucretius and his predecessors, or who would claim for our present 

 knowledge of contagia an origin altogether independent of the efforts 

 of our "forefathers" to penetrate this enigma. 



Finally, I do not know that I should agree with Prof. Virchow as 

 to what a theory is or ought to be. I call a theory a principle or con- 

 ception of the mind which accounts for observed facts, and which helps 

 us to look for and predict facts not yet observed. Every new discovery 



VOL. XIV. — 19 



