REPORT ON THE SEALS. 159 



The Brachialis anticus is situated on the outer surface of the humerus, and arises from its 

 external surface behind the deltoid ridge, and by a bundle of fibres from the lower end of this ridge. 

 It sweeps over the anterior border of the humerus ; the posterior two-thirds of the muscle near its 

 insertion goes between the humerus and the tendon of the biceps, and is inserted into the anterior 

 border of the ulna below the coronoid process ; the bundle of fibres from below the deltoid ridge 

 ends by forming the anterior third of the belly of this muscle, and is finally inserted into the bicipital 

 tuberosity of the radius, outside the tendon of the biceps. 



In Arctocephalus gazella it is in two parts. The inner part arises from the deltoid ridge between 

 its two lips, having the tendons of insertion of the pectoral and stemo-cleido-mastoid on the inner 

 lip, and the cephalo-humeral and deltoid on the outer. It extends as high as the epiphysial 

 line of the great tuber, and down to the junction of the outer lip with the inner. The outer part 

 arises from the external surface of the humerus ; and from the capsule of the shoulder-joint, which 

 is behind the outer lip of the deltoid ridge, and in front of the external border of the shaft. The 

 fibres of the inner part springing highest from the deltoid ridge of the humerus remain anterior 

 to the insertion; the lowest are posterior. It is riband-shaped, with its anterior edge in the 

 same plane as the anterior border of the radius ; it passes between the biceps and the outer part 

 to be inserted by a tendon which splits in two, behind the tendon of the biceps. The outer 

 division of the tendon is attached to the capsule of the joint over the inner surface of the head of 

 the radius, and into the tubercle .of the radius on the outer side of the tendon of the biceps. The 

 inner division of the tendon of the inner part goes behind the tendon of the biceps, and is inserted 

 into the anterior border of the ulna below the lesser sigmoid cavity opposite the radial tuberosity. 

 The outer part, with the exception of a small triangular portion at the upper end of the origin, is 

 covered by the supinator longus ; and the deltoid fills in this triangle. In front of the elbow-joint 

 it crosses from the external surface of the humerus to the internal surface of the radius, and hi 

 doing this twists, so that the anterior fibres from the shaft are external and the posterior internal. 

 It is inserted by muscular fibres into the inner surface of the capsule, over the head of the radius, 

 higher up than the inner part ; and by a tendon into the ulna outside the tendon of the inner part. 



The few fibres taking origin from the lower end of the deltoid ridge in the Phooinae, the 

 anterior surface of it in Arctocephalus, and to its inner side in Trichcchus, may be considered as the 

 equivalent of the fibres from the surface internal to the deltoid ridge in man. 



The deltoid impression of the human bone is only for the deltoid muscle. In the Seals it is 

 an eminence, and acts like an additional surface, making compensation for the smallness of the 

 humerus. In these animals it is a downward continuation of the great tuberosity, and is planted 

 upon a thick vertical wall of bone in the Phocinse and a thin translucent one in the Arctocephali, 

 The inner edge of the surface in both is flush with the inner side of the vertical plate and has a 

 straight edge ; but on the outer side it overhangs the outer surface of the shaft, and has a slight 

 projection near the middle of its surface in the Phocinas, and in the Arctocepludi a gradual expansion 

 from the middle to its inferior extremity (PI. VII. fig. 3). Roughly the eminence in the Phocinse is 

 rectangular, and in the Arctocepludi triangular with the base downwards. The surface in the Phocina.- 

 gives origin to a few fibres of the brachialis anticus and insertion for -the supra- and infraspinati. 

 teres minor, cephalo-humeral, atlanto-humeral, trapezius (anterior part), pectoral, and deltoid. This 

 surface in Arctocepliali gives origin to the brachialis (inner part), and insertion to the supraspinatus 

 (anterior and posterior parts), infraspinatus, pectoral, cephalo-humeial, sterno-cleido-mastoid, and 



