78 



THE OSTEOLOGY AND MYOLOGY 



Fig. 20.— Clavicle. 



concavity. The neck is short and wide ; above, its margin is concave ; below, straight, 

 and in direct continuation of the lower border of the bone. The glenoid is an oval, 

 somewhat elongated above, moderately concave in all directions, looking forward in the 

 plane of the bone, and obliquely downward. It terminates above as a roughened tubercle, 

 for attachment of the biceps ; a slight notch separates this prominence from the coracoid. 

 The latter is only a small knob, scarcely projecting beyond the margin of the glenoid, and 

 bent obliquely or diagonally from the postero-superior angle to the antero-inferior, and ter- 

 minating at the neck ; the supra- and infra-spinal fossae are of nearly the same superficial 

 extent. The spine is perpendicular to the plane of the bone, rises higher and higher as 

 it advances, and terminates in a large, flat, horizontally expanded, triangular acromion that 

 projects over the glenoid, and is separated from the latter by a wide and deep notch. 



Clavicle. — (Fig. 20.) The collar-bone is small and simple, with a single curvature, flat- 

 tened, and sHghtly twisted upon its axis. Both extremities are slightly knobbed. Its 



acromial connection is very loose, and it has no true articulation 

 with the sternum, being bound to the latter by long ligaments, in 

 which a small oval cartilage is obliquely placed ; this cartilage 

 scarcely being of that sort usually denominated " interarticular." 

 Humerus. — (Fig- 21.) The humerus is stout, of moderate 

 length, and with one general curve forward. The most highly developed of its several 

 well marked ridges, is that forming the outer border of the 

 bicipital groove ; it is . sharp, extends more than half-way 

 down the bone, and ends in a large, roughened tubercle for 

 the deltoid. The groove itself is shallow, from lack of a 

 well marked inner ridge, except above, where it forms a 

 decided depression between the inner and outer tuberosities. 

 The last of these is much the larger of the two, and is con- 

 tinuous with the deltoid ridge ; but both are well defined. 

 There is no proper "neck;" the shaft gradually thickens 

 above as it curves inward to support a large and very convex 

 head ; the articular surface looks in the usual direction ; its 

 contour is somewhat triangular, the three corners correspond- 

 ing to the two tuberosities and a backward prolongation. 

 The condyles and their ridges differ from each other in size 

 and shape ; the outer is shorter and broader, runs up with a 

 sharp border, which abruptly subsides to give place to a 

 smooth, rounded surface ; but a musculo-spiral groove is 

 scarcely recognizable ; the inner condyle is longer and narrower, with a straight, oblique, 

 smooth, thickened border that bridges over the large oval foramen [g). The expanded inter- 

 condylar space is smooth and flat ; its anterior surface presents a radial depression, but no 

 decided coronoid fossa; posteriorly there is a well marked olecranoid cavity. The extremities 

 of the condyles are thick and rough for muscular attachments. The lower extremity of 

 the bone curves a little forward, and the articular surfaces look in this direction as well as 

 downward. These present no special peculiarities ; they are continuous with each other ; 

 both are convex in every direction ; the ulnar reaches lower than the other, and terminates 



Fie. 21. — Left Humerus. 



