Fig. 19.—Inferior Extremity of the Left Humerus of a Felide (Lion).
1, Epitrochlea; 2, supra-epitrochlear foramen.
There exists in some mammals an osseous canal, situated above the epitrochlea, and known as the supratrochlear canal ([Fig. 19]). It is bounded by a plate of bone which at its middle portion is detached from the shaft of the humerus, and blends with the latter at both its extremities. The brachial artery and median nerve pass through the foramen.
Fig. 20.—Inferior Extremity of the Left Human Humerus, showing the Presence of a Supratrochlear Process.
1, Epitrochlea; 2, supra-epitrochlear process.
A similar condition is sometimes found, as an abnormality, in man, which presents itself under the following aspect ([Fig. 20]): an osseous prominence more or less long, in the shape of a crochet-needle—supra-epitrochlear process—situated 5 or 6 centimetres above the epitrochlea; the summit of this process gives attachment to a fibrous band, which is inserted by its other end into the epitrochlea and the internal intermuscular aponeurosis. The fibro-osseous ring thus formed gives passage to the brachial artery and the median nerve, or in case of a premature division of this artery to the ulnar branch of the same.[9]