THE HOCK. 



361 



CUT OF THE HOCK. 



ones and the cuboides by the upper heads of the shank-bone g, and the 

 splint-bones h. The cu- 

 boides is placed on the 

 external splint-bone, and 

 the cannon-bone, or prin- 

 cipal bone of the leg ; the 

 small wedge-bone is 

 principally evident on 

 the inner splint-bone, 

 not seen in the cut ; and 

 the middle wedge-bone 

 on the shank-bone only, 

 g. These bones are all 

 connected together by 

 very strong ligaments, 

 which prevent disloca- 

 tion, but allow a slight 

 degree of motion between 

 them, and the surfaces 

 which are opposed to 

 each other are thickly 

 covered by elastic car- 

 tilage. 



Considering the situa- 

 tion and action of this 

 joint, the weight and 

 stress thrown upon it 

 must be exceedingly 

 great, and it is necessarily 

 liable to much injury in 

 rapid and powerful mo- 

 tion. What are the pro- 

 visions to prevent inj ury ? 

 The grooved or pulley- 

 like heads of the tibia and 

 the astragalus, received 

 deeply into one another, 

 and confined by power- 

 ful ligaments, admitting 

 freely of hinge-like ac- 

 tion, but of no side 

 motion, to which the joint would otherwise be exposed in rapid movement, 

 or on an uneven surface. A slight inspection of the cut will show that the 

 stress or weight thrown by the tibia a on the astragalus 6, does not descend 

 perpendicularly, but in a slanting direction. By this much concussion is 

 avoided, or more readily diffused among the different bones; and, the joint 

 consisting of six bones, each of them covered with elastic cartilage, and 

 each admitting of a certain degree of motion, the diminished concussion is dif- 

 fused among them all, and thereby neutralised and rendered comparatively harm- 

 less. Each of these bones is covered not only by cartilage, but by a mem- 

 brane secreting synovia ; so that, in fact, these bones are formed into so many 

 distinct joints, separated from each other, and thereby guarded from injury, yet 

 united by various ligaments possessing altogether sufficient motion, yet bound 

 together so strongly as to defy dislocation. When, however, the work which 



