I50 THE SURGICAL ANATOMY OF THE HORSE 



condition is obtained between the first and second and between the 

 second and third phalanges. 



These muscles then act in antagonism to the flexors of the metacarpus 

 and digit. It so happens that in paralysis of the musculo-spiral nerve 

 then there follows inability of these muscles, so that when the flexors 

 act on the limb the foot is drawn backwards, and in complete flexion 

 the sole is directed upwards. Upon relaxation of the flexors, the 

 extensors being paralysed, the foot falls to the ground and rests on the 

 toe. It remains so, the knee, fetlock, and interphalangeal joints being 

 markedly flexed, and the animal is unable to progress, since activity 

 of the extensor pedis and extensor metacarpi magnus muscles is 

 particularly essential to the drawing of the limb forwards in order that 

 the foot may rest with the sole on the ground, as in the method of 

 progression. 



After a while the inactive muscles atrophy, so that in advanced cases 

 we find above the elbow, instead of the prominent, rounded, nicely 

 moulded elevation normally present, a marked depression due to the 

 wasting of the muscle bellies. The skin over this part is in a 

 loose fold, and the elbow appears now dropped to a greater degree 

 than it really is, owing to the alteration in the appearance of the 

 area above it. 



The rounded prominence on the anterior aspect of the upper third 

 of the forearm also diminishes in size, owing to the atrophy of the 

 extensor pedis and extensor metacarpi magnus muscles. 



A peculiar feature of this disease is that when the animal is placed in 

 slings he does not appear to have lost complete use of the limb, for he 

 paws the ground, and may with the limb pull his bedding backwards. 

 But he never uses the limb for supporting weight. The atrophy of the 

 muscles is progressive. 



Prognosis is usually favourable, for recovery is a common result, 

 which is quite opposed to that of most of the other paralyses. In 

 incomplete or simple cases the animal may recover the use of 



