5i THE DESCENT OF MAN 



ceases to act from disease, the other increases in size, and 

 does double work. Bones increase not only in thickness, 

 but in length, from carrying a greater weight." Different 

 occupations, habitually followed, lead to changed propor- 

 tions in various parts of the body. Thus it was ascertained 

 by the United States Commission" that the legs of the sail- 

 ors employed in the late war were longer by 0.217 of an inch 

 than those of the soldiers, though the sailors were on an 

 average shorter men; while their arms were shorter by 1.09 

 of an inch, and therefore, out of proportion, shorter in rela- 

 tion to their lesser height. This shortness of the arms is 

 apparently due to their greater use, and is an unexpected 

 result: but sailors chiefly use their arms in pulling, and not 

 in supporting weights. With sailors, the girth of the neck 

 and the depth of the instep are greater, while the circum- 

 ference of the chest, waist and hips is less, than in soldiers. 

 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. 

 Eengger" attributes the thin legs and thick arms of the 

 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. yAccording to Cranz," who lived 

 for a long time with the Eskimos, "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 



*' I have ^ven authorities for these several statements in my "Variation 

 of Animals under Domestication," vol. ii. pp. 297-300. Dr. Jaeger, "Ueber 

 das Langenwachsthum der Knochen," "Jenaiachen Zeitsehrif t, " B. v. Heft i 



^ "Investigations," etc. By B. A. Gould, 1869, p. 288. 



"8 "Saugethiere von Paraguay," 1830, s. 4. 



«• "History of Greenland," Bng. translat., 1161, vol. i. p. 230. 



