THE HOCK. 



361 



OUT OF THE HOCK. 



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

 splint-bones A. 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, 

 5f. 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 pre vent 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 b, 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'^s to defy dislocation. When, however, the work which 



