THORACIC LIMBS 



543 



FIG. 427. 



Anterior Border. 



SUPRASPINATUS. 



Greater Tuberosity. 



INFRASPINATUS. J-. 



Anterior part of 



DEEP PECTORAL. 



Bicipital Groove. 



Lesser Tuberosity. 



SUBSGAPULARIS. 



The liumerus consists of a central shaft and an upper and a lower 

 extremity. 



The Upper, or Proximal, Extremity is the larger end of the bone. 

 It is not sharply separated from the shaft, but passes gradually into 

 it below. Its greatest antero-posterior diameter is at least a third 

 greater than its greatest transverse diameter. It is deeper from before 

 backward than any other part of the bone, but its transverse width is 

 exceeded by the transverse width of the lower end. It comprises a 

 median posterior head, an outer greater tuberosity, and an inner lesser 

 tuberosity. 



The head of the humerus is the enlarged rounded swelling on the 

 posterior part of the upper extremity. When seen from above (Fig. 

 427), its outline is rudely 

 lozenge-shaped, pointed 

 in front and behind, and 

 widest at about the middle. 

 The antero-posterior di- 

 ameter is somewhat 

 greater than the trans- 

 verse diameter. The 

 convex superior surface 

 has the general outline 

 of the head. It is limited 

 in front on the outside by 

 a faint groove which curves backward and outward along the base 

 of the greater tuberosity ; it is limited on the inner side by the emar- 

 ginate upper edge of the bicipital groove, and by a roughened line 

 passing backward and inward along the base of the lesser tuberosity. 

 The surface is bounded behind, on the outside and on the inside, 

 by a roughened, jagged line which is part of the line of union of 

 the upper epiphysis with the shaft. The surface is convex in all 

 directions, but more strongly behind, where the obtusely rounded 

 point turns downward and overhangs the posterior border of the 

 bone. It is everywhere smooth ; in some specimens, however, the 

 emargination for the bicipital groove is continued backward and pro- 

 duces a shallow depression near the anterior margin. The articular 

 surface of the head of the humerus is covered with cartilage and is 

 received into the glenoid cavity of the scapula. 



Head. 



LEFT HUMERUS, PROXIMAL END. 



