MANNER OF DEVELOPMENT. 37 



the cireiimference of tlie chest, waist, and hips is less than 

 in soldiei*s. 



Whether the several foregoing modifications would be- 

 come hereditary, if the same habits of life were followed 

 during many generations, is not known, but it is probable. 

 Rengger* attributes the thin legs and thick arms of tlie 

 Payaguas Indians to successive generations having passed 

 nearly their whole lives in canoes, with their lower extremi- 

 ties motionless. Other writers have come to a similar con- 

 clusion in analogous cases. According to Cranz, f who lived 

 for a long time with the Esquimaux, " the natives believe 

 that ingenuity and dexterity in seal-catching (their highest 

 art and virtue) is hereditary; there is really something in 

 it, for the son of a celebrated seal-catcher will distinguish 

 himself, though he lost his father in childhood.^' But in 

 this case it is mental aptitude, quite as much as bodily 

 structure, which appears to be inherited. It is asserted 

 that the hands of English laborers are at birth larger than 

 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 atttiched. 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 engrav- 

 ers are liable to be short-sighted, while men lining much 

 out of doors, and especially savages, are generally long- 



* " Saugetliiere von Paraguay," 1830, s. 4. 



f " History of Greenland," Eng. translat., 1767, vol. i, p. 230. 



X " Intermarriage." By Alex. Walker, 1838, p. 377. 



" The Variation of Animals nnder Domestication," vol. i, p. 173. 



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



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



