20 



liable are — i, anaesthesia, i.e.^ that condition in which the 

 animal remains without cognizance of impressions made on 

 a surface which is normally sentient. 



Subjective hyperaesthesia, or perversion of sensibility, 

 may be either functional or organic. Functional nervous 

 disorder results generally from an abnormal state of the 

 blood. 



Muscular Paralysis, or that condition in which a cen- 

 tral volition (or the excitement equivalent to it) fails to 

 produce its normal effect of muscular contraction. 



Muscular, as well as sensational, paralysis, dependent on, 

 an affection of the brain, occurs on the opposite side to that 

 of the encephalic lesion. 



Paralysis of one side of the body is called hemiplegia. 

 Paralysis of both hind extremities is called paraplegia ; with 

 or without loss of sensation. 



Involuntary contraction of voluntary muscles, com- 

 monly called convulsions, may result from worms in the 

 bowels, indigested food in the stomach, besides other causes. 

 The three forms of spasmodic disturbance to which the 

 muscles are liable under a morbid alteration of innervation, 

 viz., the toniCj choreic and clonic, are illustrated re- 

 spectively in spasms or cramps. 



Tetanus, in horses and sheep. 

 Chorea, / • , 

 EpilepsV, [ '" -^"S^- 

 A further important pathological sub-division exists as to 

 the method of origination of those functional disturbances 

 of the nervous system, to which we have been alluding. 



The source of any of the above forms of nervous disorder, 

 hyperaesthesia, anaesthesia, muscular paralysis or convulsions, 

 may be (when not purely local) either from : 

 Central organic disease. 

 Blood perversion or defective nutrition. 

 Purely sympathetic disturbance. 

 Paralysis from central organic disease occurs from 

 softening of the brain or spinal chord, or from pressure on 

 those organs from effusion or otherwise. 



From blood, perversion in such diseases as spinal 

 meningitis. Paralysis from sympathetic disturbance occurs 

 in traumatic tetanus. 



It is far from easy in many cases to mark the diagnosis 

 between these different modes of causation of nervous symp- 

 toms ; but when the diagnosis has been made in any instance, 



