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their left leg advanced in conformity with Aristotle’s remarks, 
but he had regarded this attitude as purely conventional. 
The heart of all mammals was of like asymmetrical position 
to that of man, and its position on the left side was more 
apparent than real; the butt end being directed to the right, 
and its apex or lower end to the left. The beating of the apex 
on the left side was caused by rhythmical distension of the aortic 
arch, which thus became periodically straightened, and in re- 
laxing the apex fell.back on the left side of the thorax. It was 
quite possible and probable that, owing to the depression of the 
human thorax, (i.e.) its greater lateral than fore and aft 
diameter as compared with the compression of the same part 
in the lower animals, the apex of the heart might be thrust 
more to the left side, but he thought that the centre of gravity 
of the heart occupied a similar position in both cases. 
With regard to the cause of right-handedness, as it could 
not be due to external conditions, it seemed reasonable to attri- 
bute it to the asymmetry of the internal organs, but he thought 
that the stomach, whose cardiac end was on the left side and 
which when distended with food bulged to that side, had a 
greater claim for consideration. The greater proximity of the 
right hand to the source of arterial blood through the innom- 
inate trunk, was also worthy of consideration. The greatest 
argument against accounting for right-handedness by any of 
these methods was that while cases of reversal of the whole 
viscera were known the individuals thus characterized were not 
left-handed. Right-handedness was so universal throughout 
the human race, that he thought it could not be accounted for 
by early education, the customs of the world in all conventional 
matters being so various. If due neither to asymmetry of 
the organs of nutrition nor to education, it must be an inherited 
instinct, accidental in the sense of being due to a cause which 
has now no bearing on the species. Such a meaningless and 
persistent habit would go far to prove the unity of the human 
