7&2 



FRACTURES OF THE YERTEBRJE. 



or ossification of the inter-vertebral discs. Ercolani and many others 

 have drawn attention to the predisposing influence exerted, under 

 these circumstances, hy bony union of the vertebrae. This is probably 

 the chief reason why old horses so often suffer from fracture of the 

 vertebrae. Such fracture is commonest during dental operations 

 and the castration of thoroughbred horses. The necessity for dental 

 operations is greatest in old horses, whose bones are less resistant 

 than those of younger animals. In castration fracture generally 

 occurs at the moment when the spermatic cord is compressed, and 

 is due to the violent muscular movements. Fractures of the vertebrae 

 occur most frequently when the animal is lying on its side, seldom 

 when on its back ; Moller only met with one of the latter, and of 

 Dieckerhoff's fourteen cases only one was produced in the dorsal 

 position. 



Fig. 448. — Fracture (by crushing) of the body of a vertebra. 



Fractures may perhaps be favoured by disease of the spinal 

 column. Thummler describes abnormal fragility of the ribs and 

 vertebrae in a ten-year-old mare ; Lehnert, a case of vertebral fracture, 

 favoured by necrosis following an abscess. Paltz mentions a case 

 of osteomalacia in a horse ; after several minor fractures had occurred, 

 the 3rd lumbar vertebra was broken, with fatal results. On post- 

 mortem examination, all the bones were found excessively soft — 

 the transverse processes of the lumbar vertebrae particularly so. 

 Degive also recognises such a predisposition. 



With few exceptions the fracture occurs in the region comprising 

 the last three dorsal and the first two lumbar vertebrae, these bones 

 lying in the middle of the mobile column, which, like a stick, if 

 excessively bent, breaks most readily in the centre. But falling 

 over backwards, and other accidents, may also cause fracture of the 

 5th, 6th, 8th, or 9th dorsal, or one of the first three lumbar 

 vertebrae. 



