DESCENT OF MAN FROM SOME LOWER FORM. 153 



bodies ; and in some the deyiations were considerable. 

 He adds that the power of performing the appropriate 

 movements must have been modified in accordance with 

 the several deviations. Mr. J. Wood has recorded the 

 occurrence of 295 muscular variations in thirty-six sub- 

 jects, and in another set of the same number no less than 

 558 variations, those occurring on both sides of the body 

 being only reckoned as one. In the last set, not one body 

 out of the thirty-six was "found totally wanting in de- 

 partures from the standard descriptions of the muscular 

 system given in anatomical text-books." A single body 

 presented the extraordinary number of twenty-five dis- 

 tinct abnormalities. The same muscle sometimes varies 

 in many ways : thus Professor Macalister describes no 

 less than twenty distinct variations in the palmaris ac- 

 cessorius. 



CAtrSES OF TAEIABILITT IK DOMESTICATED MAST. 



Descent With respect to the causes of variability, 



of Man, we are in all cases very ignorant ; but we can 

 ^"^^ ■ see that in man, as in the lower animals, they 

 stand in some relation to the conditions to which each 

 species has been exposed during several generations. Do- 

 mesticated animals vary more than those in a state of 

 nature ; and this is apparently due to the diversified and. 

 changing nature of the conditions to which they have 

 been subjected. In this respect the different races of 

 man resemble domesticated animals, and so do the indi- 

 viduals of the same race, when inhabiting a very wide 

 area, like that of America. We see the influence of di- 

 versified conditions in the more civilized nations ; for the 

 members belonging, to different grades of rank, and fol- 

 lowing different occupations, present a greater range of 

 8 



