PARALYSIS OF THE HIND EXTREMITIES. 
489 
causes of the first lie within, those of the second without the vertebral 
canal. Paraplegia of the first kind, due to acute or chronic inflamma¬ 
tion of the spinal cord and its membranes, or to pressure and degenera¬ 
tive processes in the medulla spinalis, declares itself by the following 
symptoms :— 
1. Disturbance in movement, distinguished :— 
(a) By loss of strength, and 
(b) By irregularity in movement. The animals show 7 weakness, 
and rapidly become tired; the hind limbs, though able to 
sustain the weight of the body, only slightly assist in forward 
progress, and, during walking, make irregular ataxic move¬ 
ments. 
Ataxia is a form of interference with movement arising from defective 
co-oidination. The proper innervation of the separate groups of muscles 
is interfered with, in consequence of which their contractions are not 
harmoniously combined. Single groups contract too much or too little, 
others too early or too late. 
In horses and dogs, such symptoms accompany incomplete paraplegia. 
The hind feet are lifted hesitatingly and incompletely from the ground ; 
the toe is dragged, and gradually becomes worn. In the next stage 
the foot is lifted suddenly and to an abnormal height, is set down 
awkwardly and with a tapping movement, and often describes a semi¬ 
circle outwardly; the feet are placed crosswise over one another, while 
the hind-quarters roll first to one side and then to the other (plaiting the 
legs). These ataxic movements are particularly well seen when turning ; 
the animal has difficulty in backing. 
2. Sensibility and reflex irritability are generally retained, the latter 
may even be increased, causing exaggeration of the tendon reflexes. In 
general the same remarks apply here as were made in reference to 
complete paraplegia. 
8. Muscular atrophy. This is seldom seen in spinal paralysis, or is 
confined to gradual slight atrophy of both sides in consequence of 
inactivity. Degenerative atrophy and signs of degeneration never 
occur. 
4. The paraplegia of dogs, due to disease of the spinal column, is 
almost always associated with spastic contraction of the extensors, and, 
according to Dexler, with anaesthesia of the testicle. 
The non-appearance of atrophy in the spinal form of incomplete para¬ 
plegia shows that the cause lies in front of the trophic centre of the 
muscles, that is, in the posterior columns of the medulla, as paralysis 
due to brain injury generally takes the form of hemiplegia. 
The several causes of paraplegia incompleta spuria lie outside the 
spinal cord or spinal column. They sometimes consist in Assuring of 
