Ill MR. DARWIN'S WORK 



were to alter, in the minutest degree, the proportion of the 

 nervous forces now active in the two nerves which supply 

 the muscles of my glottis, I should become suddenly dumb. 

 The voice is produced only so long as the vocal chords are 

 parallel ; and these are parallel only so long as certain 

 muscles contract with exact equality ; and that again 

 depends on the equality of action of those two nerves I 

 spoke of. So that a change of the minutest kind in the 

 structure of one of these nerves, or in the structure of the 

 part in which it originates, or of the supply of blood to that 

 part, or of one of the muscles to which it is distributed, 

 might render all of us dumb. But a race of dumb men, 

 deprived of all communication with those who could speak, 

 would be little indeed removed from the brutes. And the 

 moral and intellectual difference between them and our- 

 selves would be practically infinite, though the naturalist 

 should not be able to find a single shadow of even specific 

 structural difference. 



But let me dismiss this question now, and, in conclusion, 

 let me say that you may go away with it as my mature 

 conviction, that Mr. Darwin's work is the greatest con- 

 tribution which has been made to biological science since 

 the publication of the Regne Animal of Cuvier, and since 

 that of the History of Development of Von Baer. I 

 believe that if you strip it of its theoretical part it still 

 remains one of the greatest encyclopaedias of biological 

 doctrine that any one man ever brought forth ; and I 

 believe that, if you take it as the embodiment of an 

 hypothesis, it is destined to be the guide of biological 

 and psychological speculation for the next three or four 

 generations. 



