108 



THE BONES OF THE UPPER LIMB. 



birth. The nucleus in the carpal extremity appears at the end of the 2nd year, while that of 

 t.he head is not seen till the oth or 6th year. The superior epiphysis and shaft unite about the 

 17th or 18th year ; the inferior epiphysis and shaft unite about the 20th year. 



Fig. 119. OSSIFICATION OF THE 

 RADIUS. (R. Quain.) 



A, the radius of a full-grown 

 foetus ; B, at about two years of age ; 

 C, at five years ; D, at about eighteen 

 years. 



1, shaft ; 2, ossific point of the 

 lower epiphysis ; 3, that of the upper 

 end. In D, the upper epiphysis is 

 united to the shaft, while the lower 

 is still separate. 



The ulna is ossified similarly 

 to the radius, but begins a little 

 later. The nucleus of the shaft 

 appears about the 8th week, 

 that of the carpal extremity 

 in the 4th or 5th year. The 

 upper extremity grows mainly 

 from the shaft, but at the end 

 of the olecranon a small epiphysis is formed from a nucleus which appears in the 10th 

 year. This epiphysis is united to the shaft about the 17th year ; the inferior epiphysis about 

 the 20th year. 



From what is stated above it appears that in the bones of the arm and forearm the 

 epiphyses which meet at the elbow-joint begin to ossify later, and unite with their shafts 

 earlier, than those at the opposite ends of the bones, whereas in the bones of the thigh and leg 



Fig. 120. OSSIFICATION OF THK 

 ULNA. (R. Quain.) 



A, the ulna at birth ; B. at the 

 end of the fourth year ; C, of a 

 boy of about twelve years of age ; 

 D, of a male of about nineteen 

 or twenty years. 



1, shaft; 2, nucleus of the lower 

 epiphysis ; 3, nucleus of the 

 upper epiphysis. In D, the 

 upper epiphysis is united to 

 the shaft, while the lower is still 

 separate. 



the epiphyses at the knee-joint 

 are the soonest to ossify (except 

 in the fibula) and the latest to 

 unite with their shafts. In 

 the bones of the arm and fore- 

 arm the arterial foramina are 

 directed towards the elbow ; 

 in those of the thigh and leg 



they are directed away from the knee. Thus, in each bone the epiphysis of the extremity 

 towards which the canal of the medullary artery is directed is the first to be united to 

 the shaft. It is found also that, while the elongation of the long bones is chiefly the result 

 of addition to the shaft at the epiphysial synchondroses. the growth takes place more rapidly, 

 and is continued longer, at the end where the epiphysis is last united ; and the oblique direc- 

 tion of the vascular canals is due to this inequality of growth, which causes a shifting of the 

 investing periosteum, and so draws the proximal portion of the medullary artery towards the 

 more rapidly growing end. 



The carpus is entirely cartilaginous at birth. Each carpal bone is ossified from a single 

 nucleus. The nucleus of the os magnum appears in the 1st year ; that of the unciform in 

 the 1st or 2nd year ; that of the pyramidal in the 3rd year ; those of the trapezium and the 

 lunar bone in the 5th year ; that of the scaphoid in the 6th or 7th year ; that of the 

 trapezoid in the 7th or 8th year ; and that of the pisiform in the 12th year. 





