>» BONES 
HAND AND LEFT-HANDEDNESS. 38 
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 conclusion that the superiority of the right 
hand is an acquired habit. But after stating thus much, he adds: “ 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 rather nice distinction, that, though the superiority is 
acquired, the tehdency to acquire the superiority is natural.” 
This “nice distinction ” amounts to something very like an evasion of the real diffi- 
culty, unless we assume Dr. Humphry 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 the manipulation and use of tools is manifested, are acquired, whether the right or the 
left hand be the one employed. Men are not born with carpentering, weaving, modelling 
and architectural instincts, requiring no apprenticeship or culture, like ants, bees, spiders, 
martins and beavers ; though the aptitude in mastering such arts is greater in some than 
in others. If the tendency in their practice to use the right hand is natural, that is to 
say innate or congenital, then there need be no nice distinctions in affirming it. But 
on any clearly defined physiological deductions of right-handedness from the disposition 
of the organs of motion or circulation, or any other uniform relation of the internal 
organs and the great arteries of the upper limbs, left-handedness becomes mysterious, 
if not inexplicable, unless on the assumption of a corresponding reversal of organic 
structure; for Dr. Humphry’s assertion that “in all persons the left hand may be trained 
to as great expertness and strength as the right,” is contradicted by the experience of left- 
handed persons in their efforts to apply the same training to the right hand. 
To the most superficial observer it is manifest that the anatomical disposition of the 
vital organs is not symmetrical. The heart lies obliquely, from above downwards, and 
from right to left; the trachea is on the right side, and the right and left subclavian 
veins and arteries are diversely arranged. There are also three lobes of the right lung, 
and only two of the left ; and the liver is on the right side. Here, therefore, are sources 
of difference between the right and left sides of the body, which, if subject to variation, 
offer a possible explanation of the phenomenon that has so long baffled physiologists. To 
the variations in the disposition of those organs attention has accordingly been repeatedly 
directed; as in the occasional origin of the left subclavian artery before the right, which, 
as hereafter noted, Professor Hyrtl suggested as the cause of the transfer of dexterity to 
the left limb. But instances have repeatedly occurred of the entire transposition of the 
viscera. “There are men born,” says Dr. Buchanan, “who may grow up and enjoy perfect 
health, in whom the position of all the thoracic and abdominal viscera is reversed. There 
are three lobes of the left lung and only two of the right, the liver is on the left side, and 
the heart is on the right; and so forth.” Those, and other malformations, as well as 
pathological lesions, especially if they occur in early life, may affect the relative power of 
the two sides; and Dr. Buchanan, at a later date, reported a case that came under his own 
Sec. IT., 1886. 5. 
