206 RIGHTHANDEDNESS. 



not venture to affirm more than that the one is often accompanied by 

 the other. The cases hitherto observed are, in all, so very few, that 

 without the invariable accompaniment of the left-sided lungs with left- 

 handed action, the argument is of no value. 



More recently, Dr. Humphry, of Cambridge, has discussed the cause 

 of the preferential use of the right hand, in his monograph on " The 

 Human Foot and the Human Hand," but with no very definite results. 

 Many attempts, he says, have been made to answer the question. Why 

 is man usually right-handed ? " but it has never been done quite satis- 

 factorily ; and I do not think that a clear and distinct explanation of 

 the fact can be given. There is no anatomical reason for it with which 

 we are acquainted. The only peculiarity that we can discern, is a slight 

 difference in the disposition, within the chest, between the blood-vessels 

 which supply the right and left arms. This, however, is quite insuffi- 

 cient to account for the disparity between the two limbs. Moreover, 

 the same disposition is observed in left-handed persons and in some of 

 the lower animals; and in none of the latter is there that difference 

 between the two limbs which is so general among men." Dr. Humphry 

 accordingly inclines to the view that the superiority of the riglit hand 

 is not natural, but acquired. ''All men," he says, "are not right- 

 handed; some are left-handed; some are ambidextrous; and in all 

 persons, I believe, the left hand may be trained to as great expertness 

 and strength as the right. It is so in those who have been deprived of 

 their right hand in early life ; and most persons can do certain things 

 •with the left hand better than with the right." So, far, therefore, Dr. 

 Humphry's decision would appear to be wholly in favour of the conclu- 

 sion that the superiority of the right hand is an acquired habit. But 

 after stating thus much, he sums up with this very refined distinction : 

 "Though I think the superiority of the right hand is acquired, and is 

 a result of its more frequent use, the tendency to use it in preference 

 to the left is so universal, that it would seem to be natural. I am 

 driven, therefore, to the rathor nice distinction, that, though the supe- 

 riority is acquired, the tendency to acquire the superiority is natural." 



This amounts to something very like an evasion of the real difficulty, 

 unless we assume Dr. Humphrey to mean only what Dr. Buchanan 

 states, that during the weakness of infancy and childhood the two hands 

 are used indiscriminately ; and the preferential use of one side rather 

 than the other does not manifest itself until the muscular system has 

 acquired active development. All the processes by which dexterity in 



