36 DANIEL WILSON ON THE RIGHT 
opinion,” says Dr. Pye-Smith, “that some difference between the two sides of the brain 
has to do with our preference for the right hand over the left may, perhaps, be supported 
by two very interesting cases of aphasia occurring in left-handed persons, recorded by 
Dr. Hughlings Jackson and Dr. John Ogle. In both these patients there was paralysis of 
the left side ; so that it seems likely that in these two left-handed people the right half of 
the brain had the functions, if not the structure, which ordinarily belong to the left. To 
these cases may be added a very remarkable one published by Dr. Wadham (St. George’s 
Hosp. Rep. 1869). An ambidextrous, or partially left-handed lad, was attacked with left 
hemiplegia and loss of speech; he had partly recovered at the time of his death, twelve 
months later, and then the right insula, and adjacent parts, were found softened.” 
The remarkable difference in the convolutions of different brains, and the consequent 
extent of superficies of some brains over others apparently of the same size, have been a 
matter of special observation, with results lending confirmation to the idea that great 
development of the convolutions of the brain is the concomitant of a corresponding 
manifestation of intellectual activity. But the complexity in the arrangement of these 
convolutions, and the consequent extent of superficies, often differ considerably in the 
two hemispheres of the same brain ; and it seems not improbable that left-handedness 
may prove to be traceable to certain structural differences between the right and left 
hemispheres. The variations in shape and arrangement of the convolutions in either 
hemisphere may be no more than the accidental folds of the cerebral mass, in its later 
development in the chamber of the skull; and within ordinary limits they probably 
exercise no appreciable influence on physical or mental activity. From long and 
careful observation, especially of children, I am satisfied that with the great majority, 
right-handedness is mainly the result of education, or a compliance with prevailing usage. 
Little effort would be needed with such to superinduce left-handedness. But there is a 
sufficient number of persons naturally and instinctively right-handed to determine the 
bias of the majority; though they cannot influence another, and smaller number, who 
have an equally strong and ineradicable impulse to the use of the left hand. Where, 
therefore, opportunity is afforded for examination of the brain, it is desirable that in every 
case of marked inequality between the two hemispheres, inquiry should be instituted as 
to the concurrence of a strongly pronounced right or left-handedness. 
But it has also been affirmed as the result of repeated observations, that there is often 
a decided difference in the weight of the two hemispheres of the brain. M. Broca stated 
that in forty brains he found the left frontal lobe heavier than the right ; and Dr. Boyd, 
when describing the results obtained by him from observations on upwards of 500 brains 
of patients in the St. Marylebone Hospital, says : “ It is a singular fact, confirmed by the 
examination of nearly 200 cases at St. Marylebone, in which the hemispheres were weighed 
separately, that almost invariably the weight of the left exceeded that of the right by at 
LE] 
least the eighth of an ounce.” Dr. Brown-Sequard also, as hereafter noted, makes this 
apparent excess in weight of the left hemisphere of the brain the basis of very compre- 
hensive deductions. Again Dr. Bastian affirms, as the result of careful observation, 
that the specific gravity of the grey matter from the frontal, parietal, and occipital 
convolutions, respectively, is often slighly higher on the left than it is on the right 
hemisphere. Such deductions, however, have been questioned ; and Professor Wagner 
and Dr. Thurnam both state that their careful independent investigations failed to 
