THE BONES OF THE UPPER LIMB 201 



The Carpus. 



The carpus or wrist is composed of eight short bones, which are 

 arranged in two rows, there being four bones in each row. The rows 

 are called first or proximal, and second or distal. The bones of the 

 first row, from without inwards, are called scaphoid, semilunar, 

 cuneiform, and pisiform, whilst those of the second row, in a similar 

 order, are named trapezium, trapezoid, os magnum, and unciform. 



The Scaphoid Bone. 



The scaphoid bone, which is characterized by its boat-like shape, 

 lies with its long axis oblique, the broad end being directed upwards 

 and inwards, and the narrow end or prow downwards, outwards 

 and forvs'ards. Superiorly it presents a convex articular surface 

 for the radius, which encroaches on the dorsal aspect. Injeriorly 

 it also presents a convex articular surface directed downwards, out- 



Superior Surface for Radius 



Posterior Surface 



For Semilunar 



For Os Magnam 



Inferior Surface for Trapezium 

 and Trapezoid 



Fig. 1 13 . — The Right Scaphoid Bone. 

 A, Posterior View ; B, Internal View. 



wards, and backwards, which likewise encroaches on the dorsal 

 aspect, and is divisible into two parts — an outer for the trapezium, 

 and an inner for the trapezoid. The internal surface presents two 

 articular facets — a superior, crescentic, narrow from above down- 

 wards, and looking inwards, for the semilunar, and an inferior, 

 large, concave, and directed downwards as well as inwards, for 

 the outer side of the head of the os magnum. The external aspect 

 takes the form of a rough border, extending from the radial surface 

 to the tuberosity, and giving attachment to the external lateral 

 ligament of the wrist-joint. At its lower end there is a prominent 

 tuherosity, directed forwards, which gives attachment to fibres of the 

 anterior annular ligament and abductor pollicis. The palmar surface 

 is rough and triangular. The dorsal surface, being encroached upon 

 by the superior and inferior convex articular surfaces, is reduced 

 to a rough oblique groove. • 



Articulations. — Superiorly with the radius, inferiorly with the 

 trapezium and trapezoid, and internally with the semilunar and os 

 magnum. 



