THOROUGH-PIN — THE HOCK. 285 



These cats represent the situation of some of the principal blood-vessels and nerves 

 of the hind extremities. 



In the cut of the inside of the thigh, page 2Sl, p represents the course of the prin- 

 cipal artery ; at q are blood-vessels belonging to the groin ; at r is the large cutane- 

 ous vein, or the vein immediately under the skin. The principal nerves on the fore 

 part of the inside of the thigh pursue their course at t, in the direction of the subcu- 

 taneous vein ; and those of the posterior part are seen at s, while at u are those im- 

 portant ligamentous bands at the bending of the hock which confine the tendons. 



In the cut of the outside of the tliigh, page 282, p will give the course of the an- 

 terior arteries and veins ; q that of the principal nerves, and coming into sight below ; 

 and r the bands described in the former plate. 



Also, in the cut of the outside of the shoulder and arm, p. 259, the figures 1, 2, and 

 3, designate the places of the principal artery, nerve, and vein of the leg; 4 gives 

 the subcutaneous vein running within the arm ; and 5 the subcutaneous vein of the 

 side of the chest. 



In the cut of the inside of the arm, p. 260, the lines above represent, in the order 

 from the front, the principal nerves, arteries, and veins of the shoulder and arm ; and, 

 on the muscles, k represents the principal subcutaneous vein of the inside of the arm, 

 and i the artery by which it is accompanied. 



The stifle joint is not often subject to sprain. The heat and tenderness will guide 

 to the seat of injury. Occasionally, dislocation of the patella has occurred, and the 

 horse drags the injured limb after him, or rests it on the fetlock; the aid of a veteri- 

 nary surgeon is here requisite. The muscles of the inside of the thigh have some- 

 times been sprained. This may be detected by diffused heat, or heat on the inside 

 of the thigh above the stifle. Rest, fomentations, bleeding, and physic, will be the 

 proper means of cure. 



THOROUGH-PIN. 



Mention has been made of wind-galls and their treatment. A similar enlargement 

 is found above the hock, between the tendons of the flexor of the foot and the exten- 

 sor of the hock. As from its situation it must necessarily project on both sides of 

 the hock, in the form of a round swelling, it is called a thorough-pin, a, p. 283. It is 

 an indication of considerable work, but is rarely attended by lameness. The mode 

 of treatment must resemble that for wind-galls. Although thorough-pin cannot, per- 

 haps, be pronounced to be unsoundness, it behoves the buyer to examine well a horse 

 that is disfigured by it, and to ascertain whether undue work may not have injured 

 him in other respects. 



THE HOCK. 



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

 suspected seat of lameness, and the proper formation of v/hich is essentially connect- 

 ed with the value of the horse. It answers to the ancle in the human being. 



The inferior head of the tibia is formed into two deep grooves, with three sharpen- 

 ed ridges, one separating the grooves, and the other two constituting the sides of 

 them. It is seen at a in the following cut. It rests upon a singularly-shaped bone, 

 b, the astralgus, which has two circular risings or projections, and, with a depression 

 between them, answering exactly to the irregularities of the tibia. These are re- 

 ceived and mortised into each other. At the posterior part its convex surface is re- 

 ceived into a concavity near the base of another bone, and with which it is united by 

 very strong ligaments. 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 

 tendons of powerful muscles. These bones rest on two others, the os cuhoides, d 

 (cube-formed), behind, and the larger citneifnnn or wedne-shaped bone e, in front. 

 The larger wedge-shaped bone is supported by two smaller ones. /. and these two 

 smaller ones and the cuhoides by the upper heads of the shank-bone g, and the splint- 

 Dones h. The cuhoides is placed on the external splint-bone, and the cannon-bone, 

 or principal 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 

 dislocation, but allow a slight degree of motion between them, and the surfaces which 

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



