836 DISORDERS AFFECTING MOTION AND SENSATION. 



tlie tongue may protrude without power of retraction ; there 

 is difficulty in the prehension of food and drinking of water. 

 Although mastication is impaired, the animal is still able to 

 swalloAv. Ability to stand may not be entirely lost, but power 

 of jjrogression is much affected. When motion is forced, 

 the horse is inclined to hang to the side on which the lesion 

 exists ; and the facial muscles are affected, the limbs of the 

 opposite side being paralyzed. 



When of an ephemeral character these conditions may dis- 

 appear, and the animal regain his power of locomotion in a 

 few days. Karely, however, do they recover when ability to 

 stand is absent from the first. 



Causation. — These are chiefly haemorrhages from various 

 causes, and abnormal growths interfering with the nervous 

 matter of one hemisphere. Of the few cases which I have 

 had an opportunity of watching during life and examining 

 after death, one appeared to result from haemorrhage into the 

 corpus striatum and adjoining nervous structure ; the other 

 was associated with a large cholesteatomatous tumour of the 

 choroid plexus of one lateral ventricle. In such as recover, 

 the probable cause of the hemiplegia is effusion from conges- 

 tive action, or some other agency of a transient character. 



3. Paraplegia, loss of motor-power transversely or bilaterally. 

 This is the form of motor-disturbance which in the horse is 

 the most common. From its almost constant association 

 with lesions of the cord or disturbance of functions which in 

 health are intimately related to the cord, it has come to be 

 spoken of as spinal paralysis. 



Causation. — The agencies which seem to operate in the pro- 

 duction of this condition are various, and according to their 

 supposed situation have been differently grouped. They have, 

 viewed as exhibiting lesions of the central nervous structures, 

 been spoken of as centric or organic. When appearing apart 

 from such changes, and in intimate relation with distant dis- 

 turbance or lesions, or when even these are inappreciable, they 

 have been regarded as proceed mg from peripheral irritation, 

 and named reflex or fanctional. 



1. As resulting from organic changes, we find in our patients 

 the chief of these to be — (a) Lesions, as fractures or disease of 

 the bony segments of the vertebral column, involving damage 



