52 SPRAINS. 



Curb. 



This is a swelling whicli appears at the back ot the hock, about 

 six inches below its point, in a full-sized horse. It is caused by an 

 enlargement that displaces the back tendons, nt the affected spot, 

 out of the straight line they normally preserve from point of hock 

 to fetlock (Figs. 26 and 27). 



NATURE OF THE DISEASE.— The bones at the back of the hock are 

 strongly bound together by a mass of ligamentous fibres (Fig. 28) which are 

 attached to the os calcis, to the large and small cuneiform bones, to the 

 cuboid bone, and to the heads of the splint bones and of the cannon bone 

 (Fig. 29). The rigid bar (or united column of bones) thus formed from 

 point of hock to fetlock, acts, in conjunction with the bones below the fet- 

 lock and with the hoof, as a lever for straightening out the hock when the 

 foot is on the ground ; for instance, during propulsion in the various paces, 

 in leaping, and in supporting the body when the horse rears. Here we 

 have a lever of the second order, in which the fulcrum is the ground ; the 

 weight, the resistance offered by the head of the tibia, through which bone 

 the propulsive or weight-bearing effort is transmitted ; and the power, the 

 muscles (those of the gaskin, i.e., the part between the hock and stifle) 

 which are attached to the point of the hock. It is evident that in the 

 working of this lever, strain will be thrown on the ligaments which 

 preserve its rigidity. Hence, during violent efforts to straighten the hock, 

 or to prevent it from becoming bent, while the foot is on the ground, some 

 of the 'binding ligamentous fibres are liable to give way, naturally at their 

 weakest point, which will be one or other of their points of attachment on 

 small surfaces of bone ; that of the cuboid bone or head of the outer splint 

 bone, for example. As their attachment to the back of the os calcis is of . 

 large extent, their connection with it is not likely to be severed. A serious 

 giving way of the ligaments will be followed' by displacement of the hones 

 of the hock, in wihioh case the point of the hock (upper end of the os calcis) 

 will be drawn forward, similarly to what happens in " flat foot " of man, 

 of which Fig. 30 shows an aggravated instance. We should here bear in 

 mind that the heel of man corresponds to the point of the hock of the 

 horse. In ordinary cases of curb, the injury seems to consist of the tearing 

 away, to a greater or lesser extent, of ligamentous fibres from their bony 

 attachments, with little or no displacement of the column of bones ; the 

 result being — agreeably to the remarks made by Goubaux and Barrier on 

 bone tumours, see page 229 — that a bony enlargement forms at the back of 

 the hock as a consequence of strain which has too severely taxed the 

 strength of the ligamentous brace in question. 'When the enlargement is 

 on or near the cuboid bone, the back tendons will be more or less pushed 

 out of the straight Hne which they usually form down the back of the hock, 

 and a curia (Fig. 27) will be the result. If the head of the outer splint bone 

 be the seat of injury, a jarde (Figs. 84 and 85) will be the consequence. 

 ■With respect to enlargement, from similar causes, of the head of the cannon 

 bone in producing curb, see page 245. The tendency to curb will mani- 

 festly be increased (1) by the work being of a nature to severely test the 

 strength of the said lever; (2) by the parts being unfitted, by disuse or 

 immaturity, to successfully resist violent strain ; (3) by the surfaces of 

 ligamentous attachment being comparatively small, as when the animal is 

 " tied-in below the hock ; " (4) by the muscles of the gaskin being particularly 

 strong, so that the power is increased ; and (5) by the direction of the 



