BONES. 



the suprascapular notch opens into it. The infraspinous fossa 

 is triangular. The ventral surface of the body is concave and has 

 a rounded ridge which runs from the head and neck to the in- 

 ferior angle; it also presents several rough ridges converging 

 toward the neck. [188] 



Humerus. The superior extremity comprises the head and 

 tuberosities. The head forms one-third of a spheroid, articu- 

 lates with the glenoid fossa, and looks upward, inward, and 

 slightly backward; a shallow groove (anatomical neck) sepa- 

 rates it from the tuberosities externally and is usually notched 

 opposite the small tuberosity. The great tuberosity abuts on 

 the outer side of the head and is continuous with the shaft; its 

 upper surface is quadrangular and divided into three facets, 

 upper, middle, and lower ; its outer surface is rough ; a groove 

 (bicipital) separates it anteriorly from the small tuberosity. 

 The small tuberosity lies in front of the outer half of the head, 

 has a facet (for muscular attachment) above and in front, 

 and helps form the bicipital groove. Below the tuberosities is 

 seen a constriction (surgical neck) of the shaft. [190] 



The shaft in its upper half is cylindrical. Anteriorly the 

 bicipital groove runs downward and slightly inward, its edges 

 being prolonged from the tuberosities, as their crests, and fad- 

 ing out below. The outer edge of the groove ends in the an- 

 terior limb of a rough V-shaped elevation (deltoid eminence) 

 on the outer side of the shaft, near the middle ; the posterior 

 limb of the V winds round the outer side and is continuous 

 with a ridge behind, which leads to the great tuberosity. At 

 the middle of the shaft the inner surface forms a rounded border 

 with a rough linear impression for the Coraco-brachialis. The 

 lower half of the shaft is compressed, and expanded laterally, 

 presenting two surfaces, and two lateral borders (epicondylic 

 ridges) which end inferiorly in prominences (epicondyles). 

 The internal ridge (margo medialis) , the more curved and less 

 prominent, begins in the Coraco-brachialis impression. The 

 external ridge (margo lateralis) begins behind the deltoid emi- 



[143] 



