CHAPTER IV. 

 FUNCTIONAL NERVOUS DISEASES. 



VERTIGO. MEGRIM. 



Definition.— A condition characterized by dizziness and 

 general disturbance of equilibrium (swooning). In small 

 animals it is not very commonly observed, except in dogs, 

 rabbits and pigeons. 



Etiology. — In these animals the condition is very seldom 

 found as a primary disease. It is usually secondary to other 

 diseases which it may follow. 



(a) Diseases of the brain, such as hyperemia, acute and 

 chronic, or encephalitis, often produce the symptoms of 

 vertigo, (b) Tumors, hemorrhage into the brain or mem- 

 branes, concussion of the brain, or emboli of some of the 

 cerebral bloodvessels may also produce it. (r) Defects of 

 vision, or irregular lighting in which too sudden change 

 takes place in the accommodation of the eye, have been 

 cited as causes, (d) Diseases of the middle or inner ear. 

 (e) Sudden change in the circulation of the blood in which 

 there is cerebral anemia. Tight collars may produce the con- 

 dition, or the dog pulling steadily on the leash may bring 

 it about. (/) Reflex conditions from the intestinal tract 

 (parasites or intestinal catarrh), (g) From poisoning, such 

 as ptomains, certain poisonous plants, or overdoses of alcohol 

 and other narcotics, (h) Pigeons are sometimes affected by 

 'a contagious or infectious disease having as its most promi- 

 nent symptom vertigo. Large numbers may be affected at 

 the same time. 



Symptoms.— The early indication of vertigo is charac- 

 terized by a sudden staggering gait. The animal falls 

 down, becomes unconscious. It remains in this position 

 quietly for a few moments, arises and soon assumes its 

 normal condition. The individual attack is usually of 



