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.