UTAH ACADEMY OF SCIENCES 63 
known as situs inversus. Cases of transposition are on 
record which were not correlated with left-handedness. 
Furthermorxe, all left-handed people are not character- 
ized by visceral transposition. 
Judd and others say that since the two sides of the 
brain receive their blood supply through arteries which 
are asymmetrical, that where the blood supply is larger 
to the left side of the brain, the right hand is naturally 
developed to a higher degree of dexterity; where the 
right side of the brain receives the greatest blood supply 
the person is naturally left-handed. 
This theory is invalidated by the presence of the 
anterior communicating artery, which connects the two 
cerebral arteries of the brain and forms part of the Circle 
of Willys. As a result the cerebral blood supply is 
pooled, so to speak, thus making it impossible for one 
hemisphere to receive a greater blood supply than the 
other. 
Again it is held that “in about 96 percent of all 
infants the right eye is the better-seeing eye and thus 
compels the right hand to work with it.” Stevens & 
Ducasse determined experimentally that in a majority of 
their subjects objects appearing in the right half of the 
field of vision of both eyes, are uniformly enlarged over 
objects appearing in the left half of the field of vision. 
From this they conclude that “‘by reason of the fact of a 
marked difference in the space sense of the two halves 
of the retina, objects in the right half of the field of vis- 
ion by appearing larger attract the visual attention which 
in turn leads to grasping movements with the right hand. 
The hand thus favored by earliest experience acquires a 
special skill which causes it to be used in all manual acts 
requiring the greatest precision.” A fatal objection to 
this theory is the fact that among the congenitally blind 
one finds about the same proportion of right- and left- 
handedness as among the sighted. 
In the matter of mirror-writing, by far the most 
nearly complete study of its kind was made by Fuller, of 
the University of California, who holds that “‘the knack of 
mirror-writing can be acquired by any one, although most 
of us are unaware of this latent ability.”” The simple 
explanation of mirror-writing being “that certain impul- 
