SCAPHOID. 



73 



those of one row do not correspond to those of the other. (Sed 

 Fig. 16.) 



It may be noted that, virtually, 

 continuous articular surfaces are 

 formed by the bones, by which the 

 upper row articulates with the ra- 

 dius, the lower with the metacarpus, 

 and the two rows with each other. 

 Each bone also has facets, which are 

 often deep-seated, for articulation 

 with contiguous bones, and rough- 

 ened depressions between 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 

 metacarpus. 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 

 scaphoid, lunar, and cuneiform, and 

 the trapezium behind the latter; 

 those of the lower row are the trape- 

 zoid, OS magnum, and unciform and 

 the pisiform behind the trapezoid. 



SCAPHOID. 

 (Fig. ig. 3.) 



The scaphoid, the innermost and 

 largest of the bones of the upper row, 

 presents siz surfaces, the anterior and 

 external being continuous, convex, and 

 roughened for ligamentous attachment; 

 the posterior is rough and irregular ; 

 and the internal, excavated and 

 roughened, has three projections, bear- 

 ing facets which articulate with the 

 lunar bone. The superior surface is 



Fia. 17. 

 External view of bones of right car- 

 pus, metacarpus, and digit of a Horso.. 

 1, Distal end of radius ; 2, Grooves for 

 extensor tendons ; 3, Scaphoid ; 4, 

 Lunar ; 5, Cuneiform : 6, Trapezium ; 

 7, Magnum ; 8, Unciform ; 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 pro- 

 cess. 



smooth, concavo-convex. 



