262 THE SKELETON. 



times occurs as a complication of dislocation backward of the bones of the forearm, but it is 

 doubtful if it ever occurs as an uncomplicated injury. (3) Fractures of the shaft of the ulna 

 may occur at any part, but usually take place at the middle of the bone or a little below it. 

 They are almost always the result of direct violence. (4) The styloid process may be knocked 

 off by direct violence. Fractures of the radius consist of (1 ) Fracture of the head of the bone ; 

 this generally occurs in conjunction with some other lesion, but may occur as an uncomplicated 

 injury. (2) Fracture of the neck may also take place, but is generally complicated with other 

 injury. (3) Fractures of the shaft of the radius are very common, and may take place at any 

 part of the bone. They may take place from either direct or indirect violence. (4) The most 

 important fracture of the radius is that of the lower end (Colles's fracture). The fracture is 

 transverse, and generally takes place about an inch from the lower extremity. It is caused by 

 falls on the palm of the hand, and is an injury of advanced life, occurring more frequently in the 

 female than the male. In consequence of the manner in which the fracture is caused, the upper 

 fragment becomes driven into the lower, and impaction is the result ; or else the lower fragment 

 becomes split up into two or more pieces, so that no fixation occurs. Separation of the lower 

 epiphysis of the radius may take place in the young. This injury and Colles's fracture may be 

 distinguished from other injuries in this neighborhood especially dislocation, with which it is 

 liable to be confounded by observing the relative positions of the styloid processes of the ulna 

 and radius. In the natural condition of parts, with the arm hanging by the side, the styloid pro- 

 cess of the radius is on a lower level than that of the ulna ; that is to say, nearer the ground. 

 After fracture or separation of the epiphysjs this process is on the same or higher level than that 

 of the ulna, whereas it would be unaltered in position in dislocation. 



THE HAND. 



The skeleton of the Hand is subdivided into three segments the Carpus or 

 wrist-bones ; the Metacarpus or bones of the palm ; and the Phalanges or bones 

 of the fingers. 



The Carpus. 



The bones of the Carpus (xapnoi;, the wrist), eight in number, are arranged in 

 two rows. Those of the upper row, enumerated from the radial to the ulnar 

 side, are the scaphoid, semilunar, cuneiform, and pisiform ; those of the lower 

 row, enumerated in the same order, are the trapezium, trapezoid, os magnum, and 

 unciform. 



Common Characters of the Carpal Bones. 



Each bone (excepting the pisiform) presents six surfaces. Of these the anterior 

 or palmar and the posterior or dorsal are rough for ligamentous attachment, 

 the dorsal surface being the broader, except in the scaphoid and semilunar. The 

 superior or proximal and inferior or distal are articular, the superior generally 

 convex, the inferior concave ; and the internal and external are also articular when 

 in contact with contiguous bones, otherwise rough and tubercular. The structure 

 in all is similar, consisting of cancellous tissue enclosed in a layer of compact bone. 

 Each bone is also developed from a single centre of ossification. 



Bones of the Upper Row (Figs. 204, 205). 



The Scaphoid (axdyrj, a boat ; ?<?<?c, 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, outw r ard, 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 surf ace 

 presents a narrow, rough groove, which runs the entire breadth 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 tubercle, 

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

 the anterior annular ligament of the wrist. The external surface is rough and 

 narrow, and gives attachment to the external lateral ligament of the wrist. The 



