PARALYSIS OF THE HIND LIMB. 
671 
the animal stands on the paralysed limb, because the hock is then 
excessively flexed. It is still possible, however, to place weight on the 
limb, because the Achilles tendon fixes the hock. 
The limb is advanced with all the joints excessively flexed, the foot 
being lifted very high, and set down with a hesitating (“ tapping ”) move¬ 
ment ; the action as a whole bearing some resemblance to stringhalt. 
The condition is clearly due to paralysis of the muscles at the back of 
the lower thigh. The gastrocnemii are unable to extend the hock, 
whilst the flexor perforatus is passive, 
and only affects movement through the 
medium of its peculiar tendinous appara¬ 
tus (for an illustration of this apparatus, 
see “ Rupture of the Flexor Metatarsi ”). 
Trotting is impossible. 
The muscles at the posterior surface of 
the thigh, particularly the gastrocnemii 
and flexor pedis perforans, are relaxed, 
and afterwards become atrophied. 
Nocard saw fractured pelvis in the 
horse produce symptoms closely simula¬ 
ting this lameness. Masses of callus had 
probably formed, which, by pressing on 
the internal popliteal or obturator nerves, 
caused the peculiar lameness. 
As an experiment, Moller divided a 
horse’s internal popliteal nerve just 
before its point of entry between the 
gastrocnemii. The animal at once 
assumed the position above described, 
the fetlock-joint showing plantar flexion, 
and the foot being excessively raised 
during the forward stride, though not 
quite in the same awkward way as in the other case, in which the im¬ 
mediate cause of the paralysis was perhaps more centrally situated. 
(c) Paralysis of the great sciatic nerve is followed by more general 
lameness, the muscles involved including the semi-tendinosus, semi¬ 
membranosus, and biceps femoris, and the limb is no longer capable 
of free movement. Neither the hip, stifle, nor hock joint can be flexed, 
the limb hangs limply from the hip downwards, and can neither be 
lifted nor advanced. The skin of the limb loses its sensibility. On 
enforced movement the foot is dragged along the ground with the 
phalanges bent, and in dogs, Ac., the dorsal surface of the toes is soon 
rubbed raw. When, however, by external help, the limb is placed in 
Fig. 254.—Paralysis of internal 
popliteal nerve. 
