224 SlfRGfCAL APPLIED ANATOMY. [Chap. Xl. 



bicipital groove. In no case could the two bone-ends 

 overlap. 



2. Separation of the upper epipliysis. The 



lower border of this epiphysis is represented by a 

 horizontal line crossing the bone at the base of the 

 great tuberosity, and placed between the anatomical 

 and surgical necks. It would be fairly indicated by a 

 transverse saw-cut through the widest part of the bone. 

 The three component nuclei of this epiphysis (head, 

 greater and lesser tuberosities) fuse together about the 

 fifth year, and the entire mass joins the shaft about 

 the twentieth year. The upper fragment may be 

 carried and rotated a little outwards by the muscles 

 attached to the great tuberosity, while the lower frag- 

 ment is drawn inwards and forwards by the muscles 

 inserted into the bicipital groove. Thus, a part of the 

 smooth upper end of the lower fragment commonly 

 forms a distinct projection below the coracoid process. 

 In such case the axis of the limb would be altered, and 

 the elbow carried a little from the side. Often, how- 

 ever, the displacement is solely in the antero-posterior 

 direction, the lower fragment projecting forwards. 

 So wide are the two bone surfaces at the seat of 

 injury that it is scarcely possible for them to overlap 

 one another. 



3. Surgical neck. The surgical neck is situated 

 between the bases of the tuberosities and the insertions 

 of the latissimus dorsi and teres major muscles. A 

 common displacement of parts is the following. The 

 upper fragment is carried out and rotated out by the 

 supra- and infraspinatus and teres minor. The upper 

 end of the lower fragment is drawn upwards by the 

 ileltoid, biceps, coraco-brachialis, and triceps, inwards 

 by the muscles attached to the bicipital groove, and 

 forwards by the great pectoral. Thus, it forms a 

 projection in the axilla, and the axis of the limb is 

 altered so that the elbow projects from the side. Tina 



