90 BONES OF THE UPPER LIMB. 



The Humerus is formed, like most of the long bones, from a principal centre for the 

 shaft, and from a superior and an inferior terminal epiphysis. The superior epiphysis 

 is formed by the union of two original nuclei one in the head, the other in the great 

 tuberosity, to which is added, according to Beclard and Humphry, a nucleus 

 belonging to the small tuberosity. The inferior epiphysis has four original nuclei, 

 the largest of which extends inwards from the capitellum, while a small one 

 appears at the inner part of the trochlea, and one in each supracondyloid eminence ; 

 the internal supracondyloid epiphysis remains distinct from the other three nuclei, 

 which become fused into one mass previous to their union with the shaft. 



The Radius and Ulna are each developed from an osseous centre in the middle of 

 the shaft and from an epiphysial nucleus in each extremity. The epiphyses of the 

 ulna are very small ; the upper one involves only the extremity of the olecranon. 



The Carpus is entirely cartilaginous at birth. Each Carpal bone is ossified from a 

 single nucleus. 



The Metacarpal bones and Phalanges are formed each from a principal piece and 

 one epiphysis. The ossification of the principal pieces begins at an early period. 

 In the four inner metacarpal bones the epiphysis is at the distal extremity, while 

 in the metacarpal bone of the thumb and in the phalanges it is placed at the 

 proximal extremity. 



PERIODS OF OSSIFICATION OF THE BONES OF THE UPPER LIMB. 



I. Scapula. 



The principal nucleus appears in the 7th or 8th week. 



The nucleus of the coracoid process appears in the 1st or 2nd year. 



The two nuclei of the acromion appear from the 14th to the 16th year. 



The nuclei of the inferior angle, base, and glenoid cavity, appear from the 16th 



to the 18th year. 



The coracoid process and body unite about the time of puberty. 

 The other parts unite from the 22nd to the 25th year. 



II. Clavicle. 



The principal nucleus (earliest of all bones) appears about the 6th week. 

 The epiphysis of the sternal end appears from the 18th to the 20th year. 

 The epiphysis and shaft unite about the 25th year. 



III. Humerus. 



The nucleus of the shaft appears in the 7th week. 



The nucleus of the head appears in the 2nd year. 



The nucleus of the great tuberosity appears in the 3rd year. 



The nucleus of the small tuberosity (when separate) appears in the 5th year. 



The nucleus of the capitellum appears in the 3rd year. 



The nucleus of the internal supracondyloid eminence appears in the 5th year. 



The nucleus of the trochlea appears in the llth or 12th year. 



The nucleus of the external supracondyloid eminence appears in the 13th or 



14th year. 



The nucleus of the tuberosity and head unite in the 5th year. 

 The capitellar, trochlear, and external supracondyloid nuclei unite with the shaft 



in the 16th or 1 7th year. 



The internal supracondyloid nucleus unites with the shaft in the 18th year. 

 The superior epiphysis and shaft unite in the 20th year. 



IV. Radius. 



The nucleus of the shaft appears in the 7th or 8th week. 



The nucleus of the carpal extremity appears at the end of the 2nd year. 



The nucleus of the head appears in the 5th year. 



The superior epiphysis and shaft unite about the 17th or 18th year. 



The inferior epiphysis and shaft unite about -the 20th year. 



V. Ulna. 



The nucleus of the shaft appears in the 8th week. 



