616 A MANUAL OF VETERINARY PHYSIOLOGY 



during the canter and the gallop, for the reason that it is in these 

 two paces only where one fore-leg is called upon to propel the entire 

 body weight.* The suspensory ligament sprains when insufficient 

 support is given by the tendons of tired flexor muscles to the fetlock 

 and pastern. Other ligaments in the limbs may give way through 

 an actual wrench — i.e., the subcarpal ligament in draught -horses, 

 caused by backing, or while endeavouring to prevent slipping on 

 greasy roads ; but here the ligament is caused to act in an unnatural 

 manner, both fore-legs being out in front of the body. Sprains of 

 the connecting ligaments of the pastern-joint — viz., that formed 

 between the pedis and corona — and some consider of the hock, may 

 be due to wrenches during work, and form the origin of future disease 

 in these regions. Lateral motion in either of these joints is normally 

 very limited, and wrenches passing over broken ground must occa- 

 sionally occur. Notwithstanding, the writer never remembers to 

 have seen a case of non-traumatic lameness occurring to the pedal 

 joint. The essential point, however, is that sprains of the flexor 

 tendons or suspensory ligament, due to wrenches, are practically 

 non-existent. 



The causes generally discussed above are mainly acting as the limb 

 leaves the ground ; but there are others occurring during impact, 

 producing what is conveniently termed ' concussion.' These jar the 

 foot and the bones at the lower end of the column. Of this the 

 clearest evidence is furnished by fractures of the pastern, which 

 always occur as the foot comes to the ground. When the suflraginis, 

 and rarely the corona, break, the line of fracture is in nearly every 

 case very similar, showing either that a common cause is at work, 

 or that these bones possess inherent lines of weakness. 



We have glanced at two periods during locomotion when injury 

 may occur ; there is one other, and that is the time during which 

 the body is rotating over the foot. It has been shown that the 

 fore-leg below the elbow is only intended to open and close in one 

 direction ; for instance, the foot may be made to touch the back 

 of the elbow, but it cannot be made to touch the front of the knee. 

 When the body is rotating over the foot, a point is reached where 

 the bones between the elbow and the foot are locked together 

 and rotate as one piece (see p. 609). At this time there is a great 

 strain on the locking arrangement, and considerable compression 

 of the small bones which form the end of the limb. Between the 

 suflraginis and corona the strain would appear to be the greatest, 

 on account of the small size and slender nature of the joint, and for 

 the reason that it is placed next to the centre of rotation. Clinically 

 it is recognised that this region is the seat of often incurable lameness 



There are some seats of lameness where apparently specific causes 

 are at work which should not baffle discovery. It is the upper and 

 never the lower articulatory surface of the corona which is involved 

 in ringbone, though the ends are only an inch or two apart ; it is 



* The flexor tendons of the American trotting horse give way, though 

 not so frequently as in race-horses in this country. It occurs when the 

 animal tires. It has been said above that horses do not sprain their 

 tendons while trotting, but obviously this does not refer to racing. Further, 

 the animal, when match-trotting, does not use his limbs in the same way 

 as in the common trot. On this important point, see p. 624. The writer 

 is indebted to Professor Pierre Fish, New York State Veterinary College, 

 Cornell University, and to Drs. W. Sheppard, M.R.C.V.S., and Grenside, 

 U.S.A... for information regarding lameness affecting the American trotter. 



