RIGHTHANDEDNESS. 201 



quent increase of circulation on one side more than the other; so that 

 any transposition tending to reverse this action will naturally lead to 

 greater vitality and muscular development on the opposite side. Another 

 theory traces to the reverse development of the great arteries of the 

 upper limbs, a greater flow "of blood to the left side; while a third 

 ascribes it directly to the supply of nervous force dependent on the 

 early development of the brain on one side or the other. 



So far as this line of argument prevails, it inevitably leads to the 

 result that the preference of the right hand is no mere perpetuation of 

 convenient usage, matured into an acquired, or possibly a hereditary 

 habit; but that it is, from the first, traceable to innate physical causes. 

 This, as Sir Charles Bell conceives, receives confirmation from the fact 

 already referred to, that right or left-handedness is not restricted to the 

 hand, but afi"ects the corresponding lower limb, and, as he believes, the 

 whole side. " No boy,^' he observes, "hops upon his left foot, unless he 

 be left-handed. The horseman puts the left foot in the stirrup and springs 

 from the right. We think we may conclude, that everything being 

 adapted, in the conveniences of life, to the right hand, as for example 

 the direction of the worm of the screw, or of the cutting end of the 

 augur, is not arbitrary, but is related to a natural endowment of the 

 body. He who is left-handed is most sensible to the advantages of this 

 adaptation, from the opening of the parlour door to the opening of a 

 pen-knife." And so Sir Charles Bell concludes : '' On the whole, the 

 preference of the right hand is not the efi'ect of habit, but is a natural 

 provision, and is bestowed for a very obvious purpose." Here right- 

 handedness is spoken of as " a natural endowment of the body," and 

 the whole argument is based on this assumption. But much of it would 

 be equally explicable as the result of adaptations following on an 

 acquired habit. Its full force will come under review at a later stage. 

 Meanwhile it is desirable to review the various and conflicting opinions 

 advanced by other inquirers. 



The theory of Dr. Barclay, the celebrated anatomist, is thus set forth 

 by Dr. Buchanan, from notes taken by him when a student : " The veins 

 of the left side of the trunk, and of the left inferior extremity, cross 

 the aorta to arrive at the vena cava ; and some obstruction to the flow 

 of blood must be produced by the pulsation of that artery." To this 

 Dr. Barclay traced indirectly the preferential use of the right side of 

 the body, and especially of the right hand and foot. "All motions," 

 he stated, " produce obstruction of the circulation ; and obstruction 



