THE PHENOMENA OF ORGANIC NATURE. 149 



What is it but this power of speech, of recording 

 experience, which enables men to be men — looking 

 before and after and, in some dim sense, understanding 

 the working of this wondrous universe — and which dis- 

 tinguishes man from the whole of the brute world ? I 

 say that this functional difference is vast, unfathomable, 

 and truly infinite in its consequences ; and I say at the 

 same time, that it may depend upon structural differ^ 

 ences which shall be absolutely inappreciable to us with 

 our present means of investigation. What is this very 

 speech that we are talking about ? I am speaking to 

 you at this moment, but if you 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 dis j 

 tributed, 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 ourselves would be practically in- 

 finite, 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 con- 

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

 mature conviction, that Mr. Darwin's work is the 



