48 THE ANATOMY OP THE HOESE. 



articulation. A third transverse joint is formed between the lower 

 end of the radius and the upper row. This, which is the radio-carpal 

 joint, is also provided with special ligaments. La,stly, there are four 

 ligaments which do not belong specially to any of these articulations, 

 but secure the stability of the entire composite joint, and are therefore 

 termed common. 



Movements. — The movements which take place at the carpus are 

 flexion and extension, and each of the transverse joints above-mentioned 

 is a ginglymus. When these movements are executed, however, the 

 three joints do not participate in them in an equal degree. The largest 

 share of the movement occurs at the radio-carpal articulation, and the 

 smallest between the carpus and the metacarpus ; while, as regards the 

 amount of movement, the inter carpal transverse joint occupies an inter- 

 mediate position. When the limb is flexed at the carpus it will be 

 noticed that the metacarpus and digit deviate a little outwards from the 

 plane of the fore-arm. When the limb is fully extended the lateral 

 ligaments are tightly stretched, and resist any attempts to produce 

 abduction or adduction ; but these movements can be produced when the 

 limb is fully flexed, in which position the lateral ligaments are relaxed. 

 Lateral movement, however, is not executed at this joint in any 

 appreciable degree in the living animal. The gliding movement 

 permitted between adjacent bones in each row is of importance, as 

 tending to distribute pressure, and obviate the bad effects which 

 would have been likely to result from concussion had each row been 

 a single rigid mass. 



Directions.- — The tendons which pass in relation to the joint before 

 and behind should be removed, and the ligaments should be studied 

 in the order of the following description. 



There are four ligaments common to the whole joint, viz., two lateral, 

 an anterior, and a posterior. 



The External Lateral Ligament is a cord-like band composed of a 

 deep and a superficial set of fibres, which slightly cross each other. It 

 is fixed superiorly to the external tuberosity at the lower end of the 

 radius ; and, passing over the outside of the carpus, it furnishes slips to 

 the cuneiform and unciform bones, and terminates on the head of the 

 external small metacarpal bone. The ligament is perforated by a thecal 

 canal in which the tendon of the extensor suffraginis plays. 



The Internal Lateral Ligament is fixed superiorly to the internal 

 tuberosity of the radius, and inferiorly to the heads of the large and 

 inner small metacarpal bones, furnishing slips, as it passes over the 

 carpus, to the scaphoid, magnum, and trapezoid bones. 



The Anterior Common Ligament has a flattened four-sided form. It 

 is fixed superiorly to the radius, and inferiorly to the large metacarpal 

 bone, while its lateral borders are united to the lateral ligaments. Its 



