686 Injuries to, and Concussion of, the Spinal Cord. 



Vertebral fraetui'e occurs most frefjucut ly in the horse, 

 and more rarely in other si)ecies. Tapkeii records several 

 cases in cattle. The cervical vertebrae are most commonly in- 

 volved, then the anterior Inmbar l)ones, dorsal fractnre bein*;- 

 somewhat rarer. Powerful muscular contraction nsually 

 causes fracture of the lumbar or the most posterior dorsal ver- 

 tebrjp. 



Dislocation and fracture of vertebrae cause liemorrlia,i>-es 

 between the membranes (intermeningeal hemorrhage), and in 

 many cases, as o])served by Schlesing-er, hemorrhage into the 

 tissue of the cord itself (hematomyelia). Similar hemorrhages 

 may be caused l)y external violence bringing about no actnal 

 injury to the bone. 



In rare cases, traumatism causes lesions which are only 

 detectable by microscopic examination. 



Pathogenesis. If the cord be crushed or subjected to pres- 

 sure by extra va sated blood, conductivity is destroyed both in 

 the central and peripheral directions from the seat of the lesion. 

 The conductivity may he destroyed completely, it may affect 

 only one half of the cord, or a single column; nerve function 

 will be abolished in the neighborhood of the lesion. The asso- 

 ciated nerve roots are stimulated or destroyed by dislocation 

 of the bones, and also by intermeningeal hemorrhage, which in 

 some cases involves a large section of the cord. 



Symptoms. In cases of complete cross section of the cer- 

 vical portion of the cord an\^vliere between the medulla and 

 the point of origin of the fifth and sixth pairs of cervical 

 nerves, the animal dies in a few seconds, owing to the cessa- 

 tion of respiration, because the respiratory center is cut off 

 from the nuclei of the nerve, supplying the muscles of respira- 

 tion. During the brief period elapsing between the section of 

 the cord and death, only the muscles of the head are moved. If 

 the cord is not completely destroyed, the animal may remain 

 alive for some hours, and exceptionally for several weeks, de- 

 pending upon the extent of the injury. The s;^anptoms presented 

 are those of injury to the inferior segment of the cord and also 

 in some cases l)ulbar symptoms (difficulty of swallowing, slow- 

 ing of the pulse). The body temperature may be elevated 

 (Schlesinger). 



Total destruction posterior to the cervical thickening of 

 the cord (posterior to the origin of the phrenic nerve) causes 

 paralysis and loss of sensation in the extremities, body and 

 tail. During inspiration, the thorax is not expanded, the ribs 

 are motionless, and the respiratory movements are limited to 

 the diaphragm, and through this the abdominal wall and the 

 hypochondriac region (diaphragmatic respiration). In the 

 fore quarters, the reflexes are destroyed but they persist and 

 are even exaggerated in the posterior parts of the body. In- 



