EXAMINATION 433 



1. Psychic Disturbances. — Any variation from the nor- 

 mal mental condition is manifested by abnormal excitability, 

 or abnormal depression. 



(a) Mental Excitement.— Abnormal mental excitement is 

 caused by cerebral irritation involving particularly the 

 cortex. This may be due to hyperemia, inflammatory 

 changes, excessive heat or toxic influence. The degree of 

 excitement may vary from restlessness to mania. In these 

 attacks docile animals may become vicious, bite animate 

 or inanimate objects, or even their own flesh; may stand 

 up on their hind legs, froth at the mouth, and the eyes show 

 a vacant, staring expression, conjunctiva injected. These 

 symptoms may gradually subside or they may terminate 

 in spasms and convulsions. 



(b) Mental Depression.— This may be defined as a dulling 

 of the psychic functions and may vary in degree from dul- 

 ness to coma. Mental depression is shown by the animal 

 taking less interest in its surroundings than usual, drooping 

 of the head and tail, refusing to obey commands or obeys 

 slowly or clumsily; it assumes somnolent or lethargic atti- 

 tudes or may wander aimlessly about running into objects, 

 etc. These are the milder manifestations of depression and 

 are seen in subacute and chronic diseases affecting the brain 

 chiefly the cortex. They may occur in acute infectious 

 diseases, as the early stages of distemper, rabies, in severe 

 febrile diseases, and in icterus and uremia. Other degrees 

 of mental depression are shown by somnolency, a condition 

 in which the animal appears to be asleep, but from which 

 it may be roused; or sopor, deep sleep from which it is 

 difficult to rouse the animal, and coma, or complete uncon- 

 sciousness. These conditions are produced by more severe 

 or extensive lesions. They are seen in compression of the 

 brain, cerebral hemorrhage and tumors of the brain. They 

 may be accompanied by motor disturbances in addition to 

 the mental symptoms, since these conditions may involve 

 the deeper structures of the brain as well as the cortex. 



2. 8e\sibilitv.— Disturbances of sensation may be con- 

 sidered as of two types, viz.: (a) Pathological excitation or 

 hyperesthesia and (b) pathological depression or anesthesia. 



L'N. 



