DISEASES OF THE NERVOUS SYSTEM. 229 



concussion, or sliook. or any disease in which the whole brain struc- 

 ture is involved in functional disturbance. 



Hemiplegia (paralysis of one side or half of the body). — Hemi- 

 plegia is fre(iuently the result of a tumor in the lateral ventricles of 

 the brain, softening of one hemisphere of the cerebrum, pressure 

 from extravasated blood, fracture of the cranium, or it may be due 

 to poisons in the blood or to reflex origin. AVhen heiui])legia is 

 due to or the result of a prior disease of the brain, especially of an 

 inflammatory character, it is seldom complete; it may aflfect only 

 one limb and one side of the head, neck, or muscles along the back, 

 and may pass off in a few days after the disappearance of all the 

 other evidences of the primary affection. In most cases, however, 

 hemiplegia arises from emboli obstructing one or more blood vessels 

 of the brain, or the rupture of some vessel the wall of which had 

 become weakened by degeneration and the extravasation of blood. 

 Sensibility in most cases is not impaired, but in some there is a 

 loss of sensibility as well as of motion. In some cases the bladder 

 and rectum are involved in the paralysis. 



Si/mptom^. — In hemiplegia the attack may be very sudden, and 

 the animal fall, powerless to move one side of the body; one side of 

 the lips will be relaxed; the tongue may hang out on one side of the 

 mouth: the tail curved around sideways; an inability to swallow 

 feed or water may be present, and often the urine dribbles away as 

 fast as it collects in the bladder. Sensibility of the affected side may 

 be entirely lost or only partial : the limbs may be cold and sometimes 

 unnaturally warm. In cases wherein the attack is not so severe the 

 animal may be able to maintain the standing position, but will have 

 great difficulty in moving the affected side. In such cases the animal 

 may recover from the disability. In the more severe, in which there 

 is complete loss of power of movement, recoveries are rare. 



Paraplegia (transverse paralysis of the hind extremities). — 

 Paralysis of the hind extremities is usually due to some injury or 

 inflammation alfecting the spinal cord. (See "Spinal meningitis.'' 

 p. 232, and "Myelitis," p. 233.) It may also be due to a reflex irri- 

 tation from disease of peripheral nerves, to spinal irritation or 

 congestion caused by blood poisons, etc. 



Symptoms. — When due to mechanical injury of the spinal cord, 

 from a broken back or spinal hemorrhage, it is generally progressive 

 in its character, although it may be sudden. When it is cause<l by 

 agents in the bood, it may be intermittent or recurrent. 



Paraplegia is not difficult to recognize, for it is characterized by a 

 weakness and imperfect control of the hind legs and powerless tail. 

 The urine usually dribbles away as it is formed and the manure is 

 pushed out. ball by ball, without any voluntary effort, or the passages 

 may cease entirely. When paraplegia is complete, laige and ill-con- 



