THE HUMEEUS. 



209 



ulnar and radial collateral ligaments of the elbow joint are attached proximally to 

 the medial and lateral epicondyles respectively. The proportionate length of the 

 humerus to the body height is as 1 is to 4'93-5'25. 



Nutrient foramina are usually to be seen, one at or near the surface for the insertion of the 

 coraco-brachialis, the other usually close to the posterior border of the deltoid tuberosity ; both 

 have a distal direction. Numerous vascular foramina are scattered along tne line of the anatomical 

 neck, the larger ones being situated near the proximal end of the inter-tubercular groove. The 

 vascularity of the bone is here intimately associated with the activity of its growth in this situation. 

 Connexions. The humerus articulates proximally with the scapula, and distally with the 

 radius and ulna. Embedded, as the humerus is, in the substance of the arm, its body and head 

 are surrounded on all sides. It is only at its distal part that it comes into direct relation with 

 the surface, the medial epicondyle forming a characteristic projection on the medial side of the 

 elbow; whilst the lateral epicondyle, less prominent, and the lateral epicondylic ridge can 

 best be recognised when the elbow is bent. 



At birth. About 5 years. 



About 12 years. About 16 years. 



FIG. 201. OSSIFICATION OF THE HUMERUS. 



8. Centre for lesser tubercle fuses with other centres 



about 7 years. 



9. Appears about 11 or 12 years. 



10. Distal epiphysis fuses with shaft about 16 to 17 years. 



11. Proximal epiphysis fuses with shaft about 25 years. 



with shaft 



12. Fuses with 



about 17 to 18 years. 



. Appears early in 2nd month of fostal life. 

 ; . For greater tubercle, appears 2 to 3 years. 



. For held, appears within first 6 months after birth. 



. For medial epicondyle, appears about 5 years. 



. For capitulum, appears 2 to 3 years. 

 ; . Appears about 12 years. 



. Centres for head and greater tubercle coalesce about 

 5 years. 



Sexual differences. Dwight (American Journ. of Anat. vol. iv. 1904) has shown that the 

 lead of the humerus in the female is proportionately smaller than that of the male. 



Ossification. At birth the body of the humerus is usually the only part of the 



:>one ossified, if we except the occasional presence (22 per cent.) of an ossific centre in the 



,iead. (H. R. Spencer, Journ. Anat. and PhysioL vol. xxv. p. 552.) The centre for the 



>ody makes its appearance early in the second month of intra-uterine life. Within the 



irst six months after birth a centre usually appears for the head ; this is succeeded by 



>ne for the greater tubercle during the second or third year. These soon coalesce ; and 



\ . third centre for the lesser tubercle begins to appear about the end of the third year, 



;>r may be delayed till the fourth or fifth year. These three centres are all blended by 



he seventh year, and form an epiphysis, which ultimately unites with the body about 



he age of twenty-five. It may be noticed that the proximal end of the diaphysis i 



ionical and pointed in the centre, over which the epiphysis fits as a cap, an arrangement 



vhich thus tends to prevent its displacement before union has occurred. The first centre 



o appear in the distal extremity is that for the capitulum about the second or third 



'ear. This extends medially, and forms the lateral half of the trochlear surface, the 



Centre for the medial half not making its appearance till the eleventh or twelfth year. 



