52 THE SURGICAL ANATOMY OF THE HORSE 



THE BONES OF THE CARPUS 



Usually seven bones are present in the carpus of the horse. They 

 are arranged in two rows. Those of the upper row from within out- 

 wards are the scaphoid, semilunar, cuneiform, and pisiform. In the 

 lower row we have the trapezoid, magnum, and unciform.' Occasion- 

 ally the trapezium is present in the shape of a small nodule articulated 

 to the back of the trapezoid. 



In passing the hand over the outer lateral aspect of the knee, 

 superiorly we find a well-marked elevation which corresponds to the 

 outer tuberosity at the lower extremity of the radius. . Below this is a 

 slight elevation which indicates the position of the cuneiform bone. 

 Passing downwards, we find a slight depression over the unciform, and 

 below this again is an elevation caused by the upper extremity of the 

 large metacarpal and the head of the outer small metacarpal bone. 



On the inner aspect of the joint the internal tuberosity of the distal 

 extremity of the radius forms an elevation which somewhat resembles 

 that formed by the outer tuberosity at this end of the bone. Below 

 this we have a broad, antero-posterior, slightly elevated ridge which 

 corresponds to the scaphoid. This is followed by a narrower elevation 

 which is caused by the underlying trapezoid, these two elevations being 

 separated from one another by a faint antero-posterior groove. The 

 elevation formed by the trapezoid passes almost insensibly into that 

 formed by the large and inner small metacarpal bones. 



The bones of the upper row present superiorly articular facets which 

 respond to like facets already described on the distal end of the radius. 

 Between the radius and this row there is formed a ginglymoid joint 

 which permits of a considerable degree of flexion and extension. The 

 inferior aspect of the bones of the upper row, with the exception of the 

 pisiform, also present concavo-convex facets which are moulded on to 

 the upper surfaces of the bones of the lower row. Thus the joint 



