SCAPHOID. 



73 



of one row do not correspond to those of the other, (See 

 Fig. 16.) 



It may be noted that, virtually, con- 

 tinuoQS articular surfaces are formed 

 by the bones, by which the upper row 

 articulates with the radius, the lower 

 with the metacarpus, and the two ,. 



rows with each other. Each bone r'^si^m^ -^f^'' 



also has facets, which are often deep- 

 seated, for articulation with contiguous 

 bones, and roughened depressions be- 

 tween the facets for the attachment 

 of ligaments. The true carpal 'joint, 

 or principal seat of motion, is between 

 the radius and the upper row ; there 

 is less motion between the rows, and 

 still less between the lower one and 

 the metacariDus. The lesion, termed 

 " broken knees," usually occurs where 

 there is the most extensive motion. 



Naming from within outwards, the 

 bones of the upper row are the sca- 

 phoid, lunar, and cuneiform, and the 

 trapezium behind the latter ; those of 

 the lower row are the trapezoid, os 

 magnum, and unciform, and the pisi- 

 form behind the trapezoid. 



(Fig. 16. 3.) 



The scaphoid, the innermost and 

 largest of the bones of the upper row, 

 presents six surfaces, the anterior and 

 internal being continuous, convex, and 

 roughened for ligamentous attachment; 

 the posterior is rough and irregidar ; 

 and the external, excavated and 

 roughened, has three projections, bear- 

 ing facets which articulate with the 

 lunar bone. The superior surface is 



Fig 17 

 External view of bone» of riglit car- 

 pus, metacarpus, aud digit of a Horse. 

 1, Distal end of Radius ; 2, Grooves for 

 extensor tendons ; 3, Scaphoid ; 4, 

 Lunar: 5, Cuneiform : 6, Trapezium; 

 V, Magnum ; 8, Vnciform ; 9, Great 

 Metacarpal ; 10, External small meta- 

 carpal (splint); 11, Sesamoids ; 12, 

 Proximal phalanx (os suffraginis) ; 13, 

 Median phalanx (os coronse) ; 14, Third 

 sesamoid (os naviculare) ; 15, Distal 

 phalanx (os pedis) ; 16, Basilar process. 



smooth, concavo-convex, 



