226 



THE SHOULDER GIRDLE. 



[chap. 



developed, and die acromion large and curved forwards near 

 its extremity. 



The coracoid forms a well-marked hook-like process ; it 

 contributes a very small part to the glenoid fossa, and unites 

 with the scapula about the time of puberty. 



The clavicle (Fig. 73, d) is a strongly-developed sigmoid 

 bone, remarkable for the very early age at which it com- 

 mences to ossify, in fact before any other bone of the body. 



Fig. 73. — The human sternum and right shoulder girdle at a very early period of 

 development (from an embryo 55- inches long) after Parker, \\. The dotted parts 

 are still cartilaginous ; the inner surface of the sternum and clavicle, and outer 

 surface of the scapula are represented, ost omosternum, afterwards developed 

 into the interarticular fibro-cartilaginous disk ; pc precoracoid of Parker ; <:/ shaft 

 of the clavicle ; viss mesoscapular segment of Parker ; a acromion ; c coracoid ; 

 gc glenoid cavity of scapula ; gb glenoid border; cb coracoid border; af anterior, 

 or " supraspinous," fossa ; ^^y posterior, or " infraspinous," fossa; .yj,- suprascapular 

 border. 



The outer extremity is, in the young state, tipped with 

 cartilage (the mesoscapular segment, Parker, mss), which 

 ossifies by extension of bone from the rest of the clavicle. 

 It is connected with the acromion by a small oval, flat, 

 synovial articulation. The inner end {pc) is also cartilagi- 

 nous for some time, but ossifies separately by endostosis, 



