190 



SKELETON. 



sertion of the triceps muscle, and terminates in front in a sharp 

 edge and point, which are received into the greater sigmoid ca- 

 vity of the os humeri. The coronoid process is a triangular 

 sharp ridge, much elevated, and having a large base ; on the 

 lower front of the latter is a roughness for the insertion of the 

 brachialis internus muscle. The greater sigmoid cavity forms 

 all the articular surface between the margins of the two pro- 

 cesses. It is divided, transversely, at its bottom, by a superfi- 

 cial roughness, which distinguishes the olecranon from the co- 

 ronoid portion of it. Besides which, a rising exists in its verti- 

 cal length, which is received into the corresponding depression 

 of the os hurneri. The lesser sigmoid cavity has its surface 

 continuous with that of the greater, and presents itself as a small 

 semi-cylindrical concavity, for articulating with the side of the 

 head of the radius. A small fossa, for fatty matter, exists just 

 above it. 



The carpal, or lower extremity of the ulna, presents, on the 

 side of the little finger, a process of variable length, the sty- 

 loid, from which arises the internal lateral ligament of the wrist. 

 At the radial side of this process is an articular face or small 

 head, one" surface of which looks towards the wrist, and the 

 other is in contact with the radius, being semi-cylindrical. On 

 the back of the ulna, between the styloid process and this head, 

 is a groove for a passage of the extensor carpi ulnaris. 



The body of the ulna is triangular, in consequence of three 

 ridges, which extend from the brachial to the carpal extremity. 

 The most prominent of these ridges is on its radial side, and, 

 beginning al the posterior end of the lesser sigmoid cavity, con- 

 tinues very distinct almost to the lower end; it then, however, 

 gradually subsides. From it arises the interosseal ligament. 

 Within this ridge, on the anterior or palmar face of the bone, 

 is another, more rounded, which, beginning at the internal mar- 

 gin of the coronoid process, extends down to the styloid pro- 

 cess. For the greater part of its length it gives origin to the 

 flexor profundus digitorum, but just above the carpus, the pro- 

 nator quadratus arises from it. The third ridge begins at the 

 external margin of the olecranon, and runs in a serpentine way 

 to the inferior end of the ulna, but becomes almost indistinct at 



