182 



THE OS HUMERI. 



Fig. 41.* the head is united to the bone, and the capsular 

 hgarnent of the joint is fixed. Below the fore- 

 part of its base, two tubercles stand out : the 

 smaller one, which is situated most to the inside, 

 has the tendon of the subscapularis muscle in- 

 serted into it. The larger more external pro- 

 tuberance is divided, at its upper part, into 

 three smooth plane surfaces : into the anterior 

 of which, the niusculus supra-spinatus ; into 

 the middle or largest, the infra-spinatus ; and 

 into the one behind, the teres minor, is inserted. 

 Between these two tubercles, exactly in the 

 forepart of the bone, a deep long groove is 

 formed, for lodging the tendinous head of the 

 biceps flexor cubiti ; which, after passing, in a 

 {^^'ihs" manner peculiar to itself, through the cavity of 

 the articulation, is tied down, by a tendinous 

 p sheath extended across the groove ; in which, 

 and in the neighboring tubercles, are several 

 remarkable holes, which are penetrated by the tendinous and 

 ligamentous fibres, and by vessels. On each side of this 

 groove, as it descends in the os humeri, a rough ridge, gently 

 flattened in the middle, runs from the roots of the tubercles. 

 The tendon of the pectoral muscle is fixed into the anterior of 

 these ridges, and the latissimus dorsi and teres major are 

 inserted into the internal one. A little behind the lower end 

 of this last, another rough ridge may be observed, where the 

 coraco-brachialis is inserted. From the back part of the root 

 of the largest tubercle, a ridge also is continued ; from which 

 the extensor brevis cubiti arises. This bone is flattened on the 



* The humerus of the right side ; its anterior surface. 1. The shaft of the 

 bone. 2. The head. 3. The anatomical neck. 4. The greater tuberosity. 5. 

 The lesser tuberosity. 6. The bicipital groove. 7. The anterior bicipital ridge. 

 8. The posterior bicipital ridge. 9. The rough surface into which the deltoid is 

 inserted. 10. The nutritious foramen. Jl. The rounded ])rotuherance of the 

 articular surface. 12. The pulley-like surface. 1,3. The external condyle. 14. 

 The internal condyle. 15. The external condyloid ridge. 16. The internal 

 condyloid ridge. 17. The fos.^a for the coronoid process of the ulna. 



