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CHAPTER XIV. 



THE FORE-ARM. 



Surface anatomy. At its upper half, and 

 especially in its upper third, the limb is much wider 

 in its transverse than in its antero-posterior diameter. 

 A horizontal section through this part will show a 

 cut surface that is somewhat oval in outline, and 

 is at the same time flattened in front and more 

 convex behind. This outline is best seen in muscular 

 subjects, and depends chiefly upon the development of 

 the lateral masses of muscle that descend from the 

 condyles. In the non-muscular, the limb, even in its 

 highest parts, tends to assume a rounded rather than 

 an oval outline. In women and children, also, the limb 

 is round, owing to the comparatively slight develop- 

 ment of the lateral muscular masses, and to the 

 accumulation of fat on the front and back of the limb. 

 The posterior surface of the fore-arm in a vigorous 

 subject presents along its outer border a prominence 

 formed by the supinator longus and the two radial 

 extensors, which become tendinous below the centre 

 of that border. On the lower third of this edge is a 

 slight eminence, directed obliquely downwards, out- 

 wards, and forwards, and due to the crossing of the 

 extensors of the thumb. In the middle of the pos- 

 terior surface is another elevation, running down 

 from the outer condyle, and formed mainly by 

 the extensor communis. To the inner side of this 

 eminence is a groove, well seen in the very muscular, 

 that indicates the posterior border of the ulna. The 

 ulna is subcutaneous throughout its entire extent, and 



