420 HEALTH AND DISEASE 



the impulses developed by the healthy brain fail to travel along the dis- 

 eased nerves, with the result that paralysis ensues in the part to which 

 they are distributed. 



The nerve centres and the nerves are liable to become disabled from a 

 number of diverse causes. Lack of nourishment, the consequence of in- 

 sufficient blood supply; certain poisons introduced from without or formed 

 within the body, such as lead or the accumulation of urinary or biliary pro- 

 ducts in the blood; mechanical injury or pressure; rupture of blood-vessels 

 in or upon the brain ; the formation of tumours ; inflammation and its con- 

 sequences, are all found to produce paralysis at one time or another. From 

 what has been stated it will be seen that paralysis may originate — (1) 

 in the brain (cerebral), (2) in the spinal cord (spinal), (3) in the nerves con- 

 nected with the one or the other (peripheral paralysis). Hence it follows 

 that the disease presents a considerable variety of forms, of which only 

 those of the more common kind will be considered here. 



HEMIPLEGIA 



In this form of paralysis one lateral half, the right or the left side of 

 the body, is involved. It is a rare affection in the horse, but in man it is 

 one of the most common forms of the disease, and usually appears suddenly 

 in what is commonly known as a " stroke ". The parts affected in hemi- 

 plegia are the fore and hind extremity, the muscles of the face, especially 

 those of mastication, and the tongue on one side. 



The loss of power may either be complete or incomplete, according 

 to the intensity and extent of the cause, which commonly arises out of 

 rupture of the vessels of the brain, with more or less escape of blood into 

 the tissues of the organ. 



Symptoms. — Hemiplegia is usually sudden in its onset. The affected 

 animal falls to the ground in a more or less unconscious condition, and the 

 limbs on the paralysed side are incapable of movement. In a case quoted 

 from M. Gerard by Percival the sensibility of the left, the affected side, 

 proved extremely acute. The lips and alse of the nose were drawn to 

 the right side, the contrary to that to which the head and neck turned. 

 A blowing noise was made by the air in its passage through the 

 nostrils. The left ear was paralysed and the tongue distorted. When 

 oats were laid before the horse it seized them with the right side of the 

 mouth, the left remaining motionless. There was great difficulty in masti- 

 cation, and some of the food was not swallowed, but became lodged between 

 the cheek and the molar teeth. In feeding, the horse plunged its muzzle 

 into the middle of its food and opened its mouth wide. In drinking, 



