THE HOCK. 



385 



13 called a tliorougli-pin, a. It is an indication of considerable work, but is' 

 rarely attended by lameness. The mode of treatment must resemble that 

 for wind-galls, but blistering or firing should be earlier had resort to. 



THE HOCK. 



This is a most important joint, occasionally the evident, and much 



oftener the unsuspected, 



seat of lameness, and the 



j)roper formation of which 



is essentially connected 



with the value of the 



horse. It answers to the 



ankle in the human being. 



The inferior head of 



'the tibia is formed into 



two deep grooves, Avith 



three sharpened ridges, 



one separating the gi-ooves, 



and the other two consti- 

 tuting the sides of them. 



It is seen at a in the ac- 

 companying cut. It rests 

 upon a singulai'ly-shaped 

 bone, h, the astragalus, 

 which has two circular 

 risings or projections, and, 

 with a depression between 

 them, answering exactly 

 to the irregularities of the 

 tibia. At the posterior 

 part, its convex surface is 

 received into a concavity 

 near the base of another 

 bone, and with which it is 

 united by very strong liga- 

 ments. This bone, c, is 

 called the os calcis, or bone 

 of the heel, and it projects 

 upwards, flattened at its 

 sides, and receives, strongly 

 implanted into it, the ten- 

 dons of powerful muscles. 

 These bones rest on two 

 others, the os cuboldes, d 

 (cube-formed), behind, and 

 the larger cuneiform or wedge-shaped bone, e, in front. The larger Avedge- 

 shaped bone is supported by two smaller ones, /", and these two smaller 

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

 sphnt-bones, h. The cuboides is placed on the external splint-bone, and 

 the cannon-bone, or principal bone of the leg ; the small wedge-bone is 

 principally resting on the inner splint-bone, not seen in the cut; and the 

 middle Avedge-bone on the shank-bone onlv, q. These bones are all 

 connected together by very strong ligaments, which prevent dislocation 

 but allow a slight degree of motion betAveen them, and the surfaces Avhicli 

 are opposed to each other are thickly covered by elastic cartilage. 



c c 



