74 



THE B0JSE8. 



Fig. 42. 



outwards, is seen iloB posterior crest of the furrow of torsioH, wJiicli separates the 

 latter from the posterior face of the bone. The int&iialface of the body of 

 the humerus, rounded from side to side, is not, separated from the anterior 

 and posterior faces by any marked line of detoarcation. It ofFers, near its 

 middle, a depressed scabrous process for the insertion of the adductor 

 muscles — teres major and great dorsal — of the arm. Towards its inferior 

 third it shows the nutritive foramen of the bone. 



Extremities. — These are distinguished into superior and inferior. Both 

 are slightly curved, the first backwards, the second forwards, a disposition 

 which tends to give to the humerus the form of an S. 



The superior extremity is the most volunjinous, and has three thick 

 eminences ; a posterior, external, and inteAal. The 

 first constitutes the head of the humerus; it is a 

 very slightly-detached articular eminence, rounded 

 like the segment of a sphere, and corresponding ta~ 

 the glenoid cavity of the scapula, which is too small 

 to receive it entirely. The external eminence, named 

 the trochiter, large trochanter, and gfeat tuberosity, com- 

 prises three portions,' named the summit, convexity, and 

 crest of the great tuberosity. The internal eminence, 

 the trochin, little trochanter, or small tuberosity, also 

 presents three distinct portions, which, by their posi- 

 tion, correspond exactly with the three regions of 

 the large trochanter : these are so many muscular 

 facets. 



The great and small trochanters are separated 

 from one another in front by a channel called the 

 bicipital groove, because the superior tendon of the 

 biceps muscle glides over it; it consists pf two 

 vertical grooves with a- median ridge between 

 them. 



The inferior extremity of the humerus has an 

 articular surface corresponding to the radius and ulna. 

 This surface, elongated transversely, convex from' 

 before backwards, and of greater extent witiin than 

 without, exhibits two trochlea separated by an antero- 

 posterior relief. 



The -median or. internal trochlea, the deepest, is 



limited internally by a kind of voluminous condyle, 



which corresponds to the inner lip of the humeral 



external trochlea is bordered 



POSTEEIOE VIEW OF THE 

 EIGHT HUMERUS. 



2, Exteraal tuberosity ; 3, 

 Articular head of the 

 bone; 4, External tu- 



trochlea of Man.- 



fi'^^V J' outwardly by a sl3 



bercle and 



Body or shaft of the i„ ,i j" i ,." 



bone; 10, Condyloid !°*.H ??"^y^'' °^ . 

 behmd this articul; 



olecranian (or con-^- - 



rf..the olecranon in the exteni 



'■~\ eminences, the ey" 



frst represents. 



3imen-"','i-f^Maj 



salient lip, which corresponds 



lumerus of Man. Above and 



jface is a wide deep fossa, the 



Q named because it lodges the 



^nts of the fore-arm. It is 



fj is less elevated than the 



and the second the epi- 



'tqve the inner trochlea, 



s''^ the coronoid pro- 



ip this reason, it 



ikastly, at the 



•"face is 



