HAND AND LEFT-HANDEDNESS. 37 
confirm the results arrived at by M. Broca and Dr. Boyd. From the weighing of the two 
hemispheres of eighteen distinct brains, Professor Wagner found the right hemisphere 
the heavier in ten, and the left in six cases, while in the remaining two they were of 
equal weight. Dr. Thurnam, without entering into details, states that the results of his 
weighings did not confirm Dr. Boyd’s observations ; adding that “ fresh careful observa- 
tions are certainly needed before we can admit the general preponderance of the left 
hemisphere over the right.” Though the two hemispheres of the brain are sufficiently 
distinct, they are united at the base ; and even with the most careful experimenters, the 
section through the cerebral peduncles and the corpus callosum is so delicate an opera- 
tion that a very slight bias of the operator’s hand may affect the results. That a differ- 
ence however is occasionally demonstrable in the weight of the two hemispheres is 
unquestionable, and encourages further observation with a view to ascertain definitely 
how far the evidence is in accordance with the hypothesis of left-handedness being 
referable to an exceptionally greater action of the right side of the brain. It is in full 
accordance with what has already been aflirmed as to the very partial prevalence of any 
strongly defined bias in the majority for the preferential use of either hand, that many 
brains should come under the notice of careful observers where little or no difference can 
be found between the two hemispheres. But weight is not the only element of variation. 
Dr. Bastian, in “ The Brain as an Organ of Mind,” draws attention to the unsymmetrical 
development of the two hemispheres as one of the most notable peculiarities of the human 
cerebrum. This is not only the case with reference to the number and arrangement of 
the convolutions, but it has been noted by various anatomists that the left hemisphere 
is very frequently slightly longer than its fellow. Nor are the distinct functions and 
the independent action of the two hemispheres of the brain by any means limited to the 
range of action now under review. 
Among the higher cerebral functions, the power of articulate speech has been assigned 
to the left hemisphere ; and Dr. Broca located it specifically in the third left convolution. 
Commenting on this, Dr. Bastian remarks: “It has been thought that a certain more 
forward condition of development of the left hemisphere—as a result of hereditary right- 
handedness recurring through generation after generation,—might gradually become 
sufficient to cause the left hemisphere to take the lead in the production of speech- 
movements. Some little evidence exists, though at present it is very small, to show that 
it is left-handed people more especially who may become aphasic by a lesion of the right 
third frontal gyrus.” Dr. Bastian further assumes it to be indisputable that the greater 
preponderance of right-hand movements in ordinary individuals must tend to produce a 
more complex organization of the left than of the right hemisphere ; and this both in its 
sensory and motor regions. With the left-handed, however, so many motives are constantly 
at work tending to call the right hand into play, that the compensating influences must in 
their case tend to check any inequality in the development of the two hemispheres. As to 
the supposed greater liability of left-handed people to aphasia, I have failed to find any 
confirmation of this idea. But here it will be seen that, while Dr. Bastian recognises a 
correlation between the development of one or other cerebral hemisphere and the greater 
dexterity of the opposite hand, he is inclined to regard right or left-handedness as the 
cause, rather than the effect. 
Dr. Brown-Sequard, who strongly favours the idea of superiority, both in size and 

