THE BONES OF THE UPPER LIMB 



m. THE BONES OF THE UPPER LIMB. 



The upper limb is arranged in four divisions, namely, the pectoral 

 or shoulder-girdle, brachiuni or arm proper, antibrachium or fore- 

 arm, and manus or hand. The shoulder-girdle consists of the 

 clavicle and scapula, the brachium comprises the humerus, the 

 antibrachium is composed of the radius and ulna, and the hand 

 is subdivided into a carpus, comprising eight bones, a metacarpus, 

 consisting of five bones, and phalanges, which number fourteen. 



The Clavicle. 



The clavicle or collar-bone is situated at the lower part of the 

 neck anteriorly, where it lies above the first rib, and it extends 

 outwards and backwards from the upper border of the presternum 

 to the acromion process of the scapula. The bone presents two 

 curves, an inner or sternal, occup)dng two-thirds, with its con- 



Pectoralis Major 



Deltoid 



Acromial Facet 



Trapezius 



Fig. 98. — The Right Clavicle (Superior View). 



vexity directed forwards, and an outer or acromial, extending over 

 the outer third, with its convexity directed backwards. These 

 curves impart elasticity to the bone. The clavicle is divided into 

 a shaft and two articular extremities. 



The shaft is somewhat quadrilateral over its inner two- thirds, 

 and compressed from above downwards over its outer third. The 

 superior surface is for the most part narrow, but externally it becomes 

 broad. At its inner end, near the postero-superior border, it pre- 

 sents a rough ridge, about i| inches long, for the origin of the 

 clavicular head of the stemo-cleido-mastoid. At its outer ex- 

 panded part it is encroached upon by the tendinous fibres of the 

 trapezius and deltoid. Elsewhere it is covered by the skin, fascia, 

 and platysma myoides. The anterior surface is convex over its 

 inner two-thirds, and concave over its outer third, where it is 

 reduced to a mere rough border. Over the inner haJf it is rough 

 for the origin of the clavicular portion of the pectoralis major, and 

 over its outer marginal third it gives origin to the claviciilar portion 

 of the deltoid. At the inner end of the deltoid impression there 

 is sometimes a pointed projection, knowTi as the deltoid spine. The 



