THE DESCENT OR ORIGIN OF MAN 55 



those of the gentry." From the correlation which exists, 

 at least in some cases," between the development of the ex- 

 tremities and of the jaws, it is possible that in those classes 

 which do not labor much with their hands and feet, the jaws 

 would be reduced in size from this cause. That they are 

 generally smaller in refined and civilized men than in hard- 

 working men or savages, is certain. But with savages, as 

 Mr. Herbert Spencer" 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;" 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 be short-sighted, while men living much out of 

 •doors, and especially savages, are generally long-sighted." 

 Short-sight and long-sight certainly tend to be inherited." 

 The inferiority of Europeans, in comparison with savages, 

 in eyesight and in the other senses, is no doubt the accumu- 

 lated and transmitted effect of lessened use during many 

 generations; for Eengger" states that he has repeatedly 

 observed Europeans, who had been brought up and spent 

 their whole lives with the wild Indians, who nevertheless 



« "Intermarriage." By Alex. Walker, 1838, p. zni. 



96 "Tjie Variation of Animals under Domeatication, " vol. i. p. 113. 



" "Principles of Biology," vol. i. p. 455. 



'8 Paget, "Lectures on Surgical Pathology," vol. ii., 1853, p. 209. 



" It is a singular and unexpected fact that sailors are Inferior to lands- 

 men in their mean distance of distinct vision. Dr. B. A. Gould ("Sanitary 

 Memoirs of the War of the Rebellion," 1869, p. 530) has proved this to be the 

 case; and he accounts for it by the ordinary range of vision in sailors being 

 "restricted to the length of the vessel and the height of the masts." 



30 "The Variation of Anim&ls under Domestication," vol. i. p. 8. 



'■ "Saugethiere von Paraguay," a. 8, 10. I have had good opportunities 

 for observing the extraordinary power of eyesight in the Puegians. See also 

 Lawrence ("Lectures on Physiology," etc., 1822, p. 404) on this same subject. 

 M. Giraud-Teulon has recently collected ("Bevue des Cours Scientifiques, " 

 1810, p. 625) a large and valuable body of evidence proving that the cause 

 of short-sight "e'est U travail assidu, de pres." 



