THE FORE ARM. 189 



The external condyle is just above the radial articular surface ; 

 it is continuous with a ridge of three or four inches long, form- 

 ing the external margin of the bone, and from it, and the ridge 

 together, arise the extensor muscles of the fore arm and hand. 

 The ridge, itself, is bounded, above, by a small spiral fossa, de- 

 scending downwards and forwards, made by the spiral artery 

 and the muscular spiral nerve. The internal condyle is placed 

 just above the internal margin of the ulnar articular surface : it 

 is much more prominent and distinct than the external, and may 

 be readily felt beneath the skin. A ridge also leads from it, 

 and extends upwards as high as the insertion of the coraco- 

 brachialis, but it is by no means so elevated as the external 

 ridge, though it is much longer. From the internal condyle, 

 and the adjoining part of the ridge, arise the flexor muscles of 

 the hand and fore arm. 



The os humeri is composed of compact and cancellated sub- 

 stance; the latter predominates at the extremities, and the former 

 in the body. 



SECT. III. OF THE FORE ARM. 



The fore arm is placed between the arm and the hand, and 

 consists in two straight bones, the Ulna and the Radius, of 

 which the former is on the same side with the little finger, and 

 the latter on that of the thumb. 



Of the Ulna, (Cubitus.} 



The ulna, though nearly strait, is not wholly so. It is 

 much larger at the upper than at the lower extremity, and in its 

 general features is triangular. It has to be considered in its 

 humeral and carpal extremities, and in its body. 



The humeral, or upper extremity, presents the olecranon pro- 

 cess at its termination ; the coronoid a little below and in front; 

 the greater sigmoid cavity between the two; and the lesser sig- 

 moid on the radial surface of the coronoid. 



The olecranon process is rough on its upper face, for the in- 



