46 DISSECTION OF THE ANTBBIOB LIMB. 



THE KNEE, OR CABPUS (PLATE 11, figS. 2 and 3). 



This is not a simple, but a composite, joint, and entering into its 

 formation there are the carpal bones, the lower extremity of the radius, 

 and the upper extremities of the bones of the metacarpus. The carpal 

 bones are arranged in two rows, or tiers, and the bones of each row are 

 firmly bound together and converted into a single piece by ligaments 

 passing between the adjacent bones. A transverse joint is then formed 

 between the upper and the lower tier. This may be called the inter- 

 carpal joint, and it is secured by special ligaments passing between the 

 two rows. Another transverse joint is formed between the lower row 

 and the heads of the metacarpal bones ; and this, which has also got 

 special ligaments, is termed the carpo-metacarpal 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. Lastly, 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 j oints 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 latera' 

 ligaments are tightly stretched, and resist any attempts to produce 

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

 limb is 'mSbj flexed, in which position the lateral ligaments are relaxed 

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

 able degree in the living animal. The gliding movement permittee 

 between adjacent bones in each row is of importance, as tending t( 

 distribute pressure, and obviate the bad eifects which would have beei 

 likely to result from concussion had each row been a single rio-id mass. 



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

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

 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 Extebnal Latebal Ligament is a cord-like band composed of i 

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

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



