118 
THE DESCENT OF MAN. 
Part L 
is certain. But with savages, as Mr. Herbert Spencer 26 
has remarked, the greater use of the jaws in chewing 
coarse, uncooked food, would act in a direct manner on 
the masticatory muscles and on the bones to which 
they are attached. In infants long before birth, the 
skin on the soles of the feet is thicker than on any 
other part of the body ; 27 and it can hardly be doubted 
that this is due to the inherited effects of pressure 
during a long series of generations. 
It is familiar to every one that watchmakers and 
engravers are liable to become short-sighted, whilst 
sailors and especially savages are generally long-sighted. 
Short-sight and long-sight certainly tend to be in- 
herited . 28 The inferiority of Europeans, in com- 
parison with savages, in eye-sight and in the other 
senses, is no doubt the accumulated and transmitted 
effect of lessened use during many generations; for 
Rengger 29 states that he has repeatedly observed Euro- 
peans, who had been brought up and spent their whole 
lives with the wild Indians, who nevertheless did not 
equal them in the sharpness of their senses. The same 
naturalist observes that the cavities in the skull for 
the reception of the several sense-organs are larger in 
the American aborigines than in Europeans ; and this 
no doubt indicates a corresponding difference in the 
dimensions of the organs themselves. Blumenbach has 
also remarked on the large size of the nasal cavities 
26 < Principles of Biology,’ vol. i. p. 455. 
27 Paget, * Lectures on Surgical Pathology,’ vol. i. 1853, p. 209. 
28 ‘ The Variation of Animals under Domestication,’ vol. i. p. 8. 
29 ‘Saugethiere von Paraguay,’ s. 8, 10. I have had good oppor- 
tunities for observing the extraordinary power of eyesight in the 
Fuegians. See also Lawrence (‘ Lectures on Physiology,’ &c., 1822, p. 
404) on this same subject. M. Giraud-Teulon has recently collected 
(‘ Revue des Cours Scientifiques,’ 1870, p. 625) a large and valuable 
body of evidence proving that the cause of short-sight, “ C’est le travail 
“ assidu , de pres.’ 
