THE CARPUS. 161 



Bones of the Upper Row. 

 SCAPHOID (Fig. 106). 



For radius. 



, _ -For ser* 



Tuberosity. 



For trapezium.' , 



\ tor os magnum. 



For trapesoid. 



FIG. 106. The left scaphoid. 



The Scaphoid (axdyy, a boat, elooc, like) is the largest bone of the first row. 

 It has received its name from its fancied resemblance to a boat, being broad 

 at one end and narrowed like a prow at the opposite. It is situated at the 

 upper and outer part of the carpus, its long axis being from above downward, 

 outward, and forward. The superior surface is convex, smooth, of triangular 

 shape, and articulates with the lower end of the radius. The inferior surface, 

 directed downward, outward, and backward, is smooth, convex, also triangular, 

 and divided by a slight ridge into two parts, the external of which articulates 

 with the trapezium, the inner with the trapezoid. The posterior or dorsal surface 

 presents a narrow, rough groove which runs the entire length of the bone and 

 serves for the attachment of ligaments. The anterior or palmar surface is concave 

 above, and elevated at its lower and outer part into a prominent rounded tuber- 

 osity, which projects forward from the front of the carpus and gives attachment to 

 the anterior annular ligament of the wrist and sometimes a few fibres of the 

 Abductor pollicis. The external surface is rough and narrow, and gives attach- 

 ment to the external lateral ligament of the wrist. The internal surface presents 

 two articular facets : of these, the superior or smaller one is flattened, of semilunar 

 form, and articulates with the semilunar ; the inferior or larger is concave, forming, 

 with the semilunar bone, a concavity for the head of the os magnum. 



To ascertain to which side the bone belongs, hold it with the superior or 

 radial convex, articular, surface upward, and the posterior surface i. e., the 

 narrow, non-articular, grooved surface toward you. The tubercle on the outer 

 surface points to the side to which the bone belongs. 1 



Articulations. With five bones: the radius above, trapezium and trapezoid 

 below, os magnum and semilunar internally. 



Attachment of Muscles. Occasionally a few fibres of the Abductor pollicis. 



SEMILUNAR (Fig. 107). 



For cuneiform. For radius. 



For 



For unciform. \ scaphoid. 



For os matjnum. 



FIG. 107. The left semilunar. 



The Semilunar (semi, half; luna, moon) bone may be distinguished by its 

 deep concavity and crescentic outline. It is situated in the centre of the upper 



1 In these directions eacli bone is supposed to be placed in its natural position that is, such a 

 position as it would occupy when the arm is hanging by the side, the forearm in a position of supi- 

 nation, the thumb being directed outward, and the palm of the hand looking forward. 

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