THE FOREARM 



379 



drawing a line from llic back of the condyle of tlie humerus till it cuts the 

 posterior edge of the sliaft of the os brachii about its middle, the line of 

 demarcation may easily be arrived at. 



The Radius forms the bulk of the os hraehii, supporting the weight of thr; 

 body upon its head, and conveying it to the 

 carpus through its lower extremity. Its shaft 

 is long, smooth, and convex anteriorly ; rough 

 for the attachment of muscles, and concave 

 posteriorly. The superior extramity is expanded 

 and presents an articular surface divided into 

 two fossae by a slight ridge, the inner of the 

 two being broader and more circular. On each 

 side of these pits is a slight projection, called 

 the lateral process, to which the corresponding 

 ligaments are attached. The hiferior extremity, 

 which is also expanded, is remarkable for the 

 variously shaped pits slightly marked on its 

 articular surface, each being intended to fit one 

 of the carpal bones of which the knee is made 

 up. There is a prominent internal lateral pro- 

 cess, and one less distinct on the outside marked 

 with a groove. 



The ulna (or ulnar division of the os brachii) 

 is much shorter than the radius, and can scarcely 

 be considered as having two extremities, its 

 lower end being cut off in an oblique direction 

 and terminating in a sharp point, so as to look 

 like a splicing of the one bone to the other. It 

 may be considered as consisting of a short body 

 (o, Fig. 26), surmounting which is the olecranon 

 process (3) behind, and the articular surface (4) 



Fio. 26.— Bones ok the Foue-Aum, Knee, Cannon, Pa8TEp.n3, 

 AND Foot. 



1. Semicircular fossa fjnned by the radius and ulna for tlie elbow 



joint. 



2. Body of the ulna. 



3. Olecranon process. 



4. Articulating surface. 



5. Body of the radius. 



6. Surface articulating witli the condyle of the hunicnis. 



7. Tubercle to which the coraco-radialis muscle is attached. 



8. Articulatory surfaces corresponding to tlie ujii^er row of knee- 



bones. 



9. Ospisifonne. "\ 



10. — cuneifonne. | 



11. — lunare. ,- Bones of the knee. 



12. — unciforme. i 



13. — magnurn. ; 



14. Metacarjjus or cannon-bone. 



1j. External small metacarpal bone. 



16. Tubercle to which the tendon of the muscle (extensor metacarpl 



rnagnus) is attached. 



17. Joint uniting with the os sufEraginis. 



18. Os suffraginis. 



19. External sesamoid bone. 



20. Os corona. 



21. Os pedis. 



22. 22. Wings of pedal bone. 



23. Os naviculare. 



