NERVOUS SYSTEM, 199 



I. Psychic Functions. 

 II. Sensibility. 

 III. Motility. 



I. Psychic Functions. 



Since the cerebrum and particularly its cortex is the seat 

 of all psychic activities, disease of the same must interfere 

 with normal tliouf^ht, feeling, and volition; movements, sen- 

 sations and perceptions of peripheral parts occur unconscious- 

 ly. The general mechanism, harmony and equilibrium of 

 muscular movements may be entirel\' intact in this condition. 

 JMental disturbances occur in a great many infectious dis- 

 eases, in febrile diseases in general, in the course of intoxica- 

 tions (poisonings) of varied kinds, and in local diseases of 

 the brain itself. 



Therefore, mental disturbances can 

 be ascribed to local causes only when 

 the possibilit}- of a general cause i s 

 eliminated. The disturbances in question consist of 

 abnormal excitability or of abnormal depression. 



Mental excitement is the result of cerebral ir- 

 ritation — as observed in acute cerebritis. Horses become 

 restless, neigh, refuse to be led, try to tear loose from the 

 halter, step to and fro, paw, climb up into the manger, are 

 anxious and easily frightened. Cattle bellow, snort, shake 

 their heads, jump around, and into the manger. Dogs mani- 

 fest their restlessness by an aimless running about, barking, 

 howling and even biting. Pigs squeal, crawl under the litter, 

 run about, climb over obstacles and jump up against walls. 

 Similar symptoms are also observed in rabies, acute tubercu- 

 lar meningitis, malignant catarrhal fever of the ox and in 

 anthrax. 



Symptoms of mental depression frequent- 

 ly follow those of excitement. The animals droop the head, 

 rest it on the crib or feeding rack, eyes half closed, take no 



