THE HUMERUS. 



85 



raigie directed downwards and backwards. The sccqndar end is broad 

 and flat, and articulates by a small oval surface with the acromion. 



Texture. — The interior of the clavicle contains coarse cancellated 

 tissue in its whole extent. Towards the middle of the shaft the spaces 

 widen out, and unite so as to form an irregular medullary cavity. 



THE HUMEKUS. 



The humerus or arm-bone extends from the scapula to the bones of 

 the forearm, with both of which it is articulated. It hangs nearly 

 vertically from the shoulder, with an inclina- 

 tion inwards towards the lower end. It is Fig- 71. 

 divisible into a superior extremity, including 

 the head, neck, and greater and smaller tuber- 

 osities ; the shaft ; and the inferior extremity, 

 including the external and internal condylar 

 eminences, and the inferior articular surface. 

 In general form it is subcylindrical and 

 slightly twisted. 



Fig. 71. — Right Humerus FROM BEFORE. (A. T.) ^ 



1, the articular head : 2, lesser tiilierosity ; 3, greater 

 tuberosity ; 4, neck ; 5, bicipital groove ; 6, inner bicipital 

 ridge, and mark of the attachment of the latissimus dorsi 

 and teres major muscles ; 7, outer bicipital ridge, and rough 

 surface of insertion of the pectoralis major, running down 

 into 7', the triangular mark of the insertion of the deltoid ; 

 8, spiral groove; 9, inner ridge of the humerus; 10, 

 trochlear articular surface ; 11, capitellum, or radial 

 condyle ; 12, epitrochlear or internal condylar eminence ; 

 13, capitellar or external condylar eminence ; 14, coronoid 

 depression or fossa. 



The siqjerior cxtremily is the thickest part of 

 the bone. The head is a largo hemispherical 

 articular elevation, directed inwards, upwards, 

 and somewhat backwards. The neck as de- 

 scribed by anatomists, is the ring of bone which 

 supports the head ; infer iorly, it passes into 

 the shaft ; superiorly, it is a mere groove be- 

 tween the head and the great tuberosity. The 

 f/reatti/hcroi^itijis a thick projection, continued 

 upwards from the external part of the shaft, 

 and reaching nearly to the level of the upper 

 margin of the head ; it is surmounted by 

 three_Jlat _ surfeces, the uppermost of which 

 gives attachment to the supraspi'natus muscle, 

 the lowest to the teres minor, and the inter- 

 mediate one to the infraspinatus muscle. 

 Separated from the great tuberosity by the 

 commencement of the bicijiital groove, the 

 ^SJJiall fid/erosifi/, rounded and prominent, looks directly forwards and 

 givts attachment to the subscapmlaris muscle. 



The shaft or hodi/, thick and cylindrical superiorly, becomes expanded 

 transversely, and somewhat three-sided iuferiorly. It is divided into 



