PRINCIPLES OF VETERINARY SURGERY 367 



matic ulcers are those which are associated with a special 

 disease, such as glanders, tuberculosis, carcinosis, etc., whose 

 numbers seem to diminish from day to day, while idiopathic 

 ulcers are still said to be results of unknown causes. Ulcers 

 are classified acording to their special characteristics, into 

 atonic, callous, fungous, inflammatory and phagadenic. 



FREQUENCY. — Ulcers are rare in the domestic ani 

 mals except in the specific maladies. They are seen in the 

 horse after carcinosis (and are commonly associated with 

 glanders. — L. A. M.). On the extremities they are some- 

 times the result of blows, and now and then they can be 

 traced to protracted decumbency. In the cat and dog they 

 are found on the surface of certain tumors and on the paws 

 and ears. The auricular canker of the dog is but an ulcer. 

 Among bovine animals working in the marshes or rice fields 

 or among those living in damp or dirty stalls, ulceration of 

 the heels and extremity of the tail, is frequently observed. 

 In the same species carcinosis may be the starting point of 

 an ulcer. 



PATHOGENESIS.— Ulcers are the result of a special 

 diathesis, vascular changes, either arterial or venous, or they 

 may be connected with nerve lesions. Brian has shown ex- 

 perimentally that perforating wounds in the paws of dogs 

 follow section of the posterior (superior) roots of the lumbar 

 and sacral nerves. Their frequency in the extremities has 

 led to the supposition that they may be the result of an im- 

 pediment of the return circulation, the tissues soaked with 

 serum and placed in conditions of impaired vitality not 

 being able to react against external morbific influences. 

 Primary lesions of the veins, arteries, nerves and sometimes, 

 the bones, are predisposing factors. The tissues supplied 

 bv these organs are themselves, more or less, seriously im- 

 paired. To use the expression of Reclus, they are "infirm 

 tissues " If a solution of continuity is Created in an insig- 



