CH&<PTE<R XL 

 DISEASES OF THE Eti<&. 



Canker. 



The term canker is certainly a convenient one, as the older authors 

 found it quite sufficient to designate a variety of affections of the ear, dis- 

 tinct in character, occurring in different locations, and arising from a 

 variety of causes. Some recent writers have attempted a different classi- 

 fication, but their selections are equally objectionable, and it seems 

 expedient to still recognize the term canker sanctioned by common 

 acceptation. 



The disease is really an inflammation of the lining membrane of the 

 auditory canal or passage, which extends from the large cavity of the ex- 

 ternal ear inward to the drum membrane. 



Causation. — Among the many causes which may be assigned as induc- 

 ing canker are cold, digestive disorders, improper food, over feeding with 

 insufficient exercise, the accumulation of the natural secretion in the ear, 

 and possibly, "blows. 



It may accompany skin diseases, or it may be a sequel of any exhaust- 

 ing illness. During a long run and when overheated, dogs will frequently 

 plunge in stagnant pools, and dirt and mud will lodge in the outer ear and 

 give rise to the affection. 



Eruptions sometimes appear on dogs suffering from a prolonged and 

 severe attack of distemper. The passages to the ears are often invaded by 

 these pustules, and canker results, 



Symptoms . —Unless the ears of dogs are frequently and carefully exam- 

 ined, the affection is likely to have existed for some days before attention 

 is attracted. The symptoms observed in an animal suffering from canker 

 are his restlessness, frequent scratching of his ear, and violent shaking of 

 his head. On examination the skin in the outermost part of the ear pas- 

 sage is found red, hot, and some swollen. 



The irritation may be confined to the parts forming the external cavity, 

 a condition designated by some as " external canker." 



