X. DISEASES OE THE SPINAL COLUMN 
AND PELVIS. 
I.—FRACTURES, LUXATIONS, AND SUB-LUXATIONS 
OF THE DORSAL AND LUMBAR VERTEBRAS. 
COMMOTIO SPINALIS. 
In the horse, fractures of the dorsal and lumbar vertebrse are not 
uncommon, either single processes being broken off, or the body and 
arch of the vertebra fractured. The first are rare and of no great conse¬ 
quence, though fractures of the superior spinous processes of dorsal 
vertebrae have been described. Fractures of the transverse and oblique 
processes rarely occur apart from injuries to the body of the bone. 
Fracture of the body is serious, because bleeding takes place into the 
vertebral canal and causes pressure paralysis. Such accidents are 
commonest in the horse, and may be produced in various ways, but are 
oftenest caused by the animal getting below some fixed object which 
prevents its rising. Vertebral fractures may also be caused by collisions, 
by the animal rearing and falling over backwards, and being violently 
stopped or started. Fracture of a lumbar vertebra has been seen to 
result from a horse striking out violently with both hind feet, from exces¬ 
sive muscular action in galloping, from a collision with a tree, &c., &c. 
It is still more frequently produced by muscular action when horses are 
cast, hence such fractures often form complications after important 
operations. In France and Belgium the general opinion is that fracture 
is produced at the moment of casting by excessive curvature upwards of 
the spinal column, but German and English opinion inclines to the 
belief that it most frequently occurs after the animal has been cast and 
is awaiting operation. A dull, crunching sound is often heard at the 
moment. Two movements are especially dangerous, and should, if 
possible, be prevented :— 
(1) Violent arching of the back. When the animal’s head is placed 
against the sternum, the longissimus dorsi is passively extended. If it 
and the ilio-psoas now contract energetically, the pressure on some one 
of the dorsal or lumbar vertebrae may be so severe as to cause fracture 
(“ crushing fracture ”), which is usually comminuted ; the body of the 
bone is almost always broken. 
