434 DISEASES OF THE BRAIN 



Hyperesthesia when observed in small animals is usually 

 due to some of the infectious diseases, and is seen in the 

 early stages of rabies, in tetanus, and in some of the milder 

 diseases of the cerebrum as hyperemia and acute cerebritis. 

 Hyperesthesia is manifested by abnormal movements of the 

 animal which are entirely out of proportion to the stimulus 

 applied. For example, slamming the door or clapping the 

 hands may so excite the animal that it will fall to the floor 

 or ground in spasms. Local or peripheral hyperesthesia is of 

 little or no importance in small animal practice. 



Anesthesia.— This is a condition in which there is a com- 

 plete loss of sensation. Hyperesthesia indicates a condition 

 in which tactile sensibility is merely decreased. Dimin- 

 ished sensibility may be general or complete, affecting the 

 entire animal, as in subacute or chronic inflammatory 

 conditions of the cortex of the brain and its coverings. It 

 may be partial or incomplete, affecting one entire side, 

 having its origin in one hemisphere, that of the opposite side. 

 Or it may be local, circumscribed, when more or less exten- 

 sive areas of the cerebrum are involved. Depression of 

 sensibility is determined by applying some stimulus, which 

 when applied to the normal animal will cause pain. To 

 test sensibility the skin is pricked with a needle or pin, 

 pinched or burned with a heated instrument. If the animal 

 fails to react, that is, does not show pain by crying out, 

 whining, or trying to get away from the irritant, the area 

 of part tested is anesthetic. 



Motility.— Disturbances of motility arising from the 

 brain vary in degree from slight incoordination to complete 

 paralysis. They will vary in extent and character, depend- 

 ing upon the location and size of the lesion. Disturbed 

 motility may be classified into (a) hyperkinesis or exag- 

 gerated action as seen in spasms and involuntary movements, 

 and (b) akinesis or decreased action such as occurs in loss 

 of the muscular sense and in paralysis. Disordered motility 

 may arise from pathological changes in the brain or in the 

 spinal cord. In examining disturbances of motility, it Us 

 sometimes impossible to locate definitely the seat of the 

 lesion, However, if the impaired function is accompanied 



