THE CAUSATION OF DISEASE. 287 



when all infants will be reared by hand. Mammary atrophy 

 is, I believe, already taking place among the npper classes.* 

 There is nothing to make it impossible that infants should, 

 by a terrific weeding-ont process, become thoroughly adapted 

 to artificial feeding, those only surviving whose digestive 

 organs varied in the direction of being able to digest arti- 

 ficial food. 



Yet another instance may be given. The teeth of many 

 nations appear to be undergoing rapid degeneration, so much 

 so, indeed, that some have supposed that man will eventually 

 be a toothless animal, requiring, as a matter of course, artificial 

 teeth for mastication. Now, although I have my doubts as to 

 whether this will ever happen, I do not for a moment doubt 

 that it could happen, and, under these circumstances, it would 

 appear as natural to wear artificial teeth as to wear boots, or to 

 eat with a knife and fork. 



From the above instances, it is obvious that a race may 

 adapt itself to certain most highly artificial forms of E. I say, 

 certain of them, not all ; for many forms of artificial E are, as 

 we have seen, necessarily fatal — that is, quite incompatible 

 with racial existence. 



Now, the fact that perfect adaptation to artificial forms of E 

 is possible, raises the question, Is there any fundamental dis- 

 tinction between a so-called " natural " E and an M artificial " E 

 to which adaptation has already occurred ? There is a strong 

 tendency to the belief (such is my experience) that as civi- 

 lization advances, and men live more and more artificially, they 

 must necessarily degenerate, and the ground for the belief is 

 that they do not lead "natural lives." But when we reflect 

 that natural selection is playing a conspicuous part among 

 civilized men, a doubt at once occurs as to the truth of this 

 assumption. For, viewed in the light of evolution, it is 

 obvious that the ' ' artificial " E does not stand in any broad 

 antithesis to the " natural " E (say that of the savage), or what 

 would be vulgarly called Nature. There is nothing intrinsically 

 peculiar in the natural E, since it differs for the different orders 

 of brutes, each species of which inhabits its own particular E, 



* It is quite possible, though not probable, that the mamma; will be retained 

 through sexual selection, even though their secretive function be lost. 



