62 TRANSACTIONS OF THE 
most instances is unverifiable and unknown to all but the 
investigator himself. 
There have been but two systematic studies made 
which deal with the hereditary aspects of left-handed- 
ness;—Jordan and Ramaley. In both instances, how- 
ever, the results point to the conclusion that left-handed- 
ness is a Mendelian recessive. In the light of this and 
other facts, it would seem that there are all degrees of 
handedness ranging from extreme left-handedness to 
extreme right-handedness with a moderate right-hand- 
edness as the mode, or the most frequent type. But our 
difficulty here, as elsewhere in this problem, is that the 
studies have been too few and all not sufficiently com- 
prehensive. 
The origin or cause of right- and left-handedness has 
been a favorite theme of the educational theorist. I shall 
mention a few typical explanations. 
It is argued by some that a child’s handedness is a 
result of imitating its parents, or that it arises from the 
mother’s constant method of carrying it. 
Again it is said that the great majority of right- 
handedness is largely the result of education. 
It is argued by Gould (8) and others that since the 
heart is the most vital organ of the body and is located 
nearer the left side, in primative warfare the shield was 
held in the left hand thus protecting the heart, while the 
right hand became the spear hand and has consequently 
acquired a dexterity which has been perpetuated through 
the ages. 
Some argue that since the viscera on the right side 
of the body are heavier than on the left side (the liver and 
lungs), this condition places the center of gravity to 
the right of the anatomical center, thus rendering the 
use of the right limbs more likely. That owing to the 
position of the arteries the blood is forced through the 
right subclavian artery under a greater pressure than 
through the left, and as a result the muscles of the right 
side are better nourished and stronger. Left-handedness 
is explained by the earlier branching off of the left sub- 
clavian artery. 
The last two theories imply that left-handedness is 
tie 1esult of a transposition of the viscera or what is | 
