iv. SKELETON OF UPPER LIMB. 151 



7. The CARPUS consists of eight small bones arranged in 

 two transverse series. 



The bones of the upper, or proximal row, are : (i) the 

 scaplwides x (or scaphoid bone) ; (2) the lunare (or semi-lunar 

 bone) ; (3) the cuneiforme (or wedge-shaped bone) ; and (4) the 

 pisifonne (or pea-shaped bone). 



The first two together form an upper convex surface which 

 fits into the distal articular cup of the radius. 



The pisiforme stands out freely, and is rather a supple- 

 mentary ossification of a tendon (a kind of extra ossification 

 often occurring in different places) than a true bone of the 

 wrist. It is a small bone. 



The bones of the lower, or distal row, are : (i) the trapezium ; 

 (2) the trapezoides ; (3) the magnum; (4) the unciforme. 



These bones together form an undulating upper articular 

 surface, there being a concavity on the radial side to receive 

 a prominence of the scaphoid, and in the middle a strong 

 convexity fitting into the cup formed by the distal sufraces 

 of the three radial (or outer) carpals of the proximal row. 



Distally, the second row of carpals presents varied surfaces 

 for the reception of the proximal ends of the bones of the 

 middle, solid, part of the hand (the metacarpus), which are 

 called metacarpals. 



The magnum is the largest bone of the distal series, while 

 the unciforme articulates with and supports two metacarpals, 

 namely, the fourth and fifth. 



The trapezium presents a saddle-shaped surface to the first 

 metacarpal, being concave in one direction and convex in 

 another. 



8. The METACARPALS are five elongated bones, each with a 

 rounded head and a base moulded to suit the surface of the 

 adjoining part of the carpus. 



The first metacarpal (that of the thumb) is shorter than the 

 others, and differs from them by its mode of ossification, its 

 epiphysis being situate only at its proximal end, while in 

 each of the other metacarpals there is an epiphysis at the 

 distal end only. 



The proximal surface of the first metacarpal is deeply 

 concave, to suit the saddle-shaped surface of the trapezium 

 its support. 



9. The thumb and four FINGERS are called "digits "in 

 zootomy, each having a further distinguishing name. 



Thus the first digit, or thumb, is termed \hzpollex. 



1 From <TKd<j>r,, a boat. 



