THE HUMERUS 



119 



the musculo-spiral groove. The internal surface lies between the anterior and 

 ulnar borders. The lower halves of the internal and external surfaces afford origin 

 to the brachiab's anticus muscle. The internal surface usually presents, about 

 5 cm. (2") above the ulnar condyle, an elongated rough surface. This is the 

 supracondyloid ridge ; it is occasionally replaced by a prominent spine of bone, 

 the supracondyloid process (fig. 125), from which a band of fibrous tissue 



Fig. 126.— Ossification of the Humerus, 



UNITES WITH THE SHAFT AT THE TWENTIETH YEAR. 

 THE UPPER EPIPHYSIS IS FORMED BY THE UNION OF 

 THE NUCLEUS FOR THE HEAD, GREATER TUBEROSITY, 

 AND THAT FOR THE LESSER TUBEROSITY. THESE 

 FORM A COMMON EPIPHYSIS BEFORE UNITING WITH 

 THE SHAFT 



SHAFT BEGINS TO OSSIFY IN THE EIGHTH WEEK OF 

 INTRA-UTERINE LIFE 



ri 



r//.. ♦ 



NUCLEUS FOR THE INTERNAL CONDYLE APPEARS AT. 



FIFTH; FUSES AT THE EIGHTEENTH YEAR 

 NUCLEUS FOR TROCHLEA APPEARS AT THE TENTH YEAR- 



i:^" 



UGLEUS FOR EXTERNAL CONDYLE APPEARS AT FOUR- 

 TEENTH YEAR 



iry NUCLEUS FOR CAPITELLUM APPEARS IN THE THIRD YEAR 



THE CENTRES FOR THE hADiAL Cuf.DVLE. 



TROCHLEA, AND CAPITELLUM UNITE TOGETHER AND FORM AN EPIPHYSIS 



WHICH FUSES WITH THE SHAFT AT THE SEVENTEENTH YEAR 



extends to the ulnar condyle, forming a ring, transmitting the median nerve and 

 the brachial artery. The nerve is not always accompanied by the artery; in some 

 instances of high division of the brachial the foramen transmits the interosseous 

 artery. The process gives origin to the pronator radii teres, and sometimes aflords 

 insertion to a part of the roraro-hrarhialis. 



The posterior surface lies between the ulnar and radial borders. It is 

 oblic^uely divided by the musculo-spiral groove. The surface above the groove 



