204 



OSTEOLOGY. 



Primary centre 

 appears about 

 2nd m. foetal life. 



Acromial centres 

 appear 15-16 yrs. ; 

 fuse about 25 yrs. 



Secondary centre for 

 coracoid appears 

 about end 1st yr. ; 

 fuses about 18 yrs. 



Appears about 



16-17 yrs. ; fus< 



about 20 yrs. 



Subcoracoid centre 

 appears 10 yrs. ; fuses 

 16-17 yrs. 



Appears about 

 17 yrs. ; fuses 

 about 20 yrs. 



coracoid process represents the epicoracoid or precoracoid of lower forms, whilst tb 

 subcoracoid centre (metacoracoid) which assists in the formation of the glenoid cavity is thi 

 reduced and vestigial remains of the stout coracoid element met with in Ornithorhynchus 

 which articulates with the sternum. 



Nutrient Foramina. Foramina for the passage of nutrient vessels are seen in different part 

 of the bone ; the most constant in position is one which opens into the infra-spinous fossa, about a] 

 inch or so from the scapular notch. Others are met with on the upper and under surfaces of th 

 spine, on the costal aspect near its deepest part, and also around the glenoid margin. 



Connexions. The scapula is not directly connected with the trunk, but articulates with th 

 lateral end of the clavicle, in union with which it forms the shoulder girdle, supporting th 

 humerus on its glenoid surface. Placed on the upper and back part of the thorax, it covers th 

 ribs from the second to the seventh inclusive. Possessed of a wide range of movement, it alter 

 its position according to the attitude of the limb, rising or falling, being drawn medially o 

 laterally, or being rotated upon itself according as the arm is moved, in various directions. Thes 

 changes in position can easily be determined by recognising the altered relations of the subcutaneou 

 and bony prominences, more especially the former, which include the spine, the acromion, and th 

 inferior half of the vertebral border. 



Ossification. Ossification begins in the body of the cartilaginous scapula about th 

 end of the second month of foetal life. At birth the head, neck, body, spine, and base o 

 the coracoid process are well defined ; the vertebral margin, inferior angle, glenoid cavity 

 acromion, and coracoid process, are still cartilaginous. The centre for the upper an< 

 anterior part of the coracoid appears in the first year, and fusion, along an oblique line leadinj 

 from the upper edge of the glenoid cavity to the conoid tubercle, is complete about th 

 fifteenth year. A separate centre (subcoracoid), which ultimately includes the superior par 



of the glenoid cavity and latera 

 part of the coracoid process 

 makes its appearance abou 

 the tenth year, and fuses witl 

 the surrounding bone abou 

 sixteen or seventeen. Up til 

 the age of puberty the ac 

 romion remains cartilaginous 

 centres, two or more in num 

 ber, then make their appear 

 ance, which coalesce and ulti 

 mately unite with the spini 

 about the twenty-fifth year 

 Failure of union may, however 

 persist throughout life (se< 

 Appendix B Variations). 



Ossification commences ir 

 the cartilage in the inferioi 

 angle about puberty, and in 

 dependency and a little later 

 along the vertebral margin, 

 fusion with the body occurring 

 at from twenty to twenty-five 

 years. 



Small scale-like epiphyses 

 make their appearance on the 

 superior surface and at the 



extremity of the coracoid, and are completed about the twentieth year. A thin epiphysial 

 plate develops over the inferior part of the glenoid cavity about sixteen or seventeen, fusion 

 being complete about eighteen or twenty years of age. 



The Humerus. 



The humerus, or bone of the arm, articulates proximally with the scapula 

 and distally with the bones of the forearm, namely, the radius and ulna. Its 

 proximal end comprises the head and greater and lesser tubercles ; its body, which 

 is longer than any of the other bones of the upper extremity, is cylindrical 

 proximally and flattened distally. At the distal extremity, which is expanded to 

 form the epicondyles on either side, it supports the trochlear and capitular articular 

 surfaces for the ulna and radius resnectivelv. 



Appears about 



16 or 17 yrs. ; 



fuses 18-20 yrs. 



Appears 16-17 

 yrs.; fuses 20- 

 25 yrs. 



Appears 16-17 yrs. 

 fuses 20-25 yrs. 

 Scapula at end of First Year. Scapula about the Age of Puberty. 



FIG. 193. OSSIFICATION OF THE SCAPULA. 



