Catching
sight of the whip, the horse sprang forward, while the man felt
an acute pain and a sense of something having given way at his
shoulder. He did not fall off, but rode a little further and was
helped to dismount. On examination a subcoracoid dislocation of
the head of the humerus was found. The explanation is that as the
weight of the whip was inconsiderable (four ounces) the inertia
of the arm converted it into a lever of the first order. Instead
of fulfilling its normal function of preventing displacement, the
coraco-acromial arch acted as a fulcrum. The limb from the
fingers to that point acted as the "long arm," and the head and
part of the neck of the humerus served as the "short arm." The
inertia of the arm, left behind as it were, supplied the power,
while the ruptured capsular ligament and displacement of the head
of the bone would represent the work done.
Congenital Dislocations.--The extent and accuracy of the
knowledge possessed by Hippocrates on the subject of congenital
dislocations have excited the admiration of modern writers, and
until a comparatively recent time examples of certain of the
luxations described by him had not been recorded. With regard,
for instance, to congenital dislocations at the shoulder-joint,
little or nothing was known save what was contained in the
writings of Hippocrates, till R.
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