258 PAr.TICULAR LAMENESSES. 



A muscle, when iiiHamed, or when atrophied, loses its power 

 of contractility and its tone ; and in this form of lameness the 

 shoulder bulges outwards when the weight of the animal is 

 thrown upon the lame side, because the muscles which bind the 

 shoulder, and limit the great extent of motion between the 

 scapula and humerus, are no longer able to perform their 

 functions. So much then for the shoulder of the off side limb ; 

 and we must now endeavour to explain how "shoulder-slip" 

 can occur in the near side, or that which is placed upon the 

 land, and higher than its fellow during ploughing. 



The second function of these muscles is to' prevent the out- 

 ward bulging of the shoulder-joint, more particularly the head of 

 the humerus, — a condition of the joint which occurs always 

 when a limb is placed upon higher ground than its fellow, as 

 any one might see by watching a horse working in the plough. 

 There is a bulging outward, a contortion in fact, at every step 

 the animal takes ; the parts are thrown out of their equilibrium, 

 first into a state of undue relaxation, by the upward pressure of 

 the humerus, then of undue extension, by the outward bulging. 

 Again, both fore feet may be occasionally in the furrow, and 

 the hind ones also. This, with slipping in and out, and the 

 inequality of the land, brings on, particularly in the young horse, 

 a state of irritation which finally terminates in inflammation 

 and atrophy. 



It is seldom that any but young horses suffer from this lame- 

 ness, as older horses become used to their work, and are able 

 to avoid injuring themselves. Great care is therefore required 

 in bringing the young horse gradually to his work, — in fact, " to 

 break him in " with due caution, by placing him at the side of 

 a steady, quiet old horse ; one that will not outpace him, nor 

 fatigue him in his work. When an animal becomes fatigued 

 he loses command over his action, becomes unsteady in his gait, 

 and is thus rendered liable to sprain himself. 



Symptoms. — In some cases there will be swelling and heat 

 over the course of the muscles, upon the outer surface of the 

 scapula, and in the joint itself; but in the majority of cases 

 actual lameness does not occur until the muscles have become 

 considerably atrophied, and instead of swelling, there will be 

 a wasting of the shoulder. There will be a hollow space upon 

 either side of the scapular spine, extending its whole length. 



