Of the tuberosities of the head of the humerus, one is situated on the external aspect--it is the great tuberosity, or _trochiter_; the other is placed internally--it is the small tuberosity, or _trochin_. The great tuberosity is divided into three parts--summit, convexity, and crest; these different parts give insertion to the muscles of the shoulder. We recollect that the facets (anterior, middle, and posterior) of the great tuberosity of the humerus in man give attachment to the muscles of the same region. The head of the humerus in the human body projects above the tuberosities. We shall see afterwards, when dealing with some special quadrupeds, that in some of these, on the other hand, the tuberosities are on a higher level than the articular head of the bone. Between the two tuberosities is the bicipital groove. In man, the superior extremity of the humerus, although covered by the deltoid, reveals its presence by elevating the corresponding portion of the latter. In quadrupeds, the anterior part of this extremity, although similarly covered by muscular bundles, produces a prominence under the skin. This prominence is situated at the summit of the angle formed by the opposing directions of the scapula and the bone of the arm, and constitutes what is known by the name of the _point of the shoulder_, or of the _point of the arm_. The inferior extremity, transversely enlarged, presents an undulating articular surface, which reminds us of the trochlea and the condyle of the human humerus; on which, however, the condyle is more sharply defined from the trochlea. In the human skeleton, the internal lip of the trochlea descends lower than the external; and also lower than the condyle. In the bear, the cat, and the dog, it is the same. In the ox and the sheep, the condyle is lower than the trochlea, but only very little lower. In the horse the arrangement is still the same, but a little more accentuated. On the lateral parts of this extremity we find: internally, a prominence, the epitrochlea; and, externally, another, the epicondyle. It is from this latter that the crest arises, which, passing upwards, forms the posterior limit of the groove of torsion.