46 THE ANATOMY OF THE HORSE. 



The Synovial Membrane will be seen to line the inner face of the 

 anterior and lateral ligaments, but at the back part of the joint there 

 is no ligament and the membrane is supported by the muscles. If the 

 finger be passed backwards and upwards, it will enter a process of the 

 synovial capsule which extends upwards into the olecranon fossa, where 

 a pad of fat intervenes between it and the anconeous muscle. Just 

 behind the external lateral ligament, the membrane lines the origin of 

 the flexor metacarpi externus. On the inner side of the joint, behind 

 the internal lateral ligament, the membrane lines the tendons of origin 

 of the middle and internal flexors of the metacarpus, and fc of the super- 

 ficial and deep flexors of the digit. This disposition of the synovial 

 capsule will be rendered more evident by cutting the above-mentioned 

 muscles a few inches below the joint, and then turning their tendons of 

 origin upwards. 



Directions. — The humerus being now T completely severed from the 

 radius and ulna, the mode of union of these latter bones should be 

 examined. 



The Radio-ulnar Articulation. — In the adult animal the bones of 

 the fore-arm are fused together below the radio-ulnar arch by ossifica- 

 tion of the inter-osseous fibres which in the young animal are interposed 

 between the two bones. Above the arch, however, the fibres interposed 

 between the bones do not ossify except in a very old animal, but persist 

 as an inter-osseous ligament. The union of the two bones is further 

 maintained by arciform fibres passing on each side from the one bone to 

 the other, and blending with the lateral ligaments of the elbow. At the 

 upper part of their opposed surfaces, the two bones respond to each 

 other by two small synovial facets, which, however, have no special 

 synovial membrane, but are lubricated by processes from the synovial 

 capsule of the elbow-joint. 



Movements. — These are inappreciable, the limb of the horse being 

 fixed in a condition of pronation. 



THE KNEE OR CARPUS (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 row r s, or tiers, and the bones of each row 

 are firmly bound together and converted into a single piece by liga- 

 ments 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 



