PARALYSIS OF RADIAL NERVE. 
517 
to enable it to carry weight; when passively extended, however, the limb 
is able to sustain the body. On moving the horse the triceps muscles 
appear relaxed. They fail to contract, and after some time atrophy. 
In incomplete radial paralysis the weight of the body can be supported 
provided sufficient muscular power exist to extend the joint. When, 
therefore, the animal moves slowly and on a smooth surface, nothing 
particular is visible, though lameness appears immediately the horse 
meets with a slight incline or with any obstacle. In such case the foot 
is not sufficiently extended, it strikes against the obstacle and the leg 
collapses, so that the horse may fall. Depending on the degree to which 
the nerve or muscle is affected, this stumbling occurs more or less fre¬ 
quently ; sometimes it is only seen after exertion on soft or uneven 
Fig. 194.— First portion of the stride in a case of paralysis of the radial nerve. The animal 
was recovering. 
ground. When the lameness diminishes after having long existed, the 
animals instinctively adopt a peculiar way of moving. In stepping out 
they slide the foot forwards with exaggerated action of the shoulder 
muscles, so as to compensate for the defect in that of the extensors. 
The lameness is characterised by stumbling, particularly on uneven 
ground, and later by a sliding motion of the foot when the limb is 
extended. 
Cases of radial paralysis due to fractured first rib can sometimes be 
diagnosed by drawing the affected limb towards the opposite side of the 
body, and sharply returning it to its former position. By applying the 
