DISEASES OF THE SPINE AND ITS COVERINGS. 497 



are those in which the loss of power in muscles, or the 

 insensibility of parts, constitute very special and pathog- 

 nomonic symptoms. Paralysis may affect a part from in- 

 jury to a single nerve, but more commonly we observe 

 either the hind legs affected, as in paraplegia, or one side 

 of the body, as in hemiplegia, or both sides of the body, 

 whether partially or completely. "We thus have the same 

 loss of power varying in degree and extent ; and that same 

 absence of motion or sensation may indicate the existence 

 of diseases varying greatly from each other. Paralysis, 

 therefore, is but a symptom of disease, and the usual 

 symptom in affections of the spinal cord and its meninges. 



In all cases of disease or injury of the cord, or spinal 

 canal implicating the cord, the paralysis occurs in the 

 parts to which all the nerves are distributed, which originate 

 or are connected with the cord behind the seat of injury or 

 disease. If there be an injury to the sacrum, the tail alone 

 may be paralysed ; if the lumbar vertebrae are broken, the 

 paralysis affects the hind quarters. If the cervical portion 

 of the spinal cord is implicated low down, the fore limbs, 

 as well as the hind ones, are deprived of power and sensi- 

 bility ; and if the cord is affected high up, near its point of 

 union with the brain, the phrenic nerves can transmit no 

 more impressions, the respiratory centre is injured, and the 

 animal can no longer breathe. 



The various kinds of paralysis differing principally in 

 the extent to which the limbs and trunk are paralysed, are 

 well illustrated by the symptoms which follow the various 

 fractures of the spinal column. 



When an animal falls on its head and breaks its neck 



close up to its attachment with the head, or when an 



animal is pithed, by dividing with a knife the medulla ob- 



longata or upper part of the cord, there is instant suffoca- 



VOL. tt. 4 c 



