368 



PRINCIPLES OF VETERINARY SURGERY 



nificant trauma, a slight inflammation, or fugacious dermati- 

 tis, an ulcer may be promptly evolVed. The anatomical ele- 

 ments, already diseased, having become deeply injured, are 

 threatened with impending death. The trophic lesions on 

 the extremities of neurotomized horses give a very clear 

 idea of the phenomena presenting themselves in the evolu- 

 tion of an ulcer. Previous pathological conditions which 

 diminish the vitality of the tissues, lessen the nutritive phe- 



FiG. 34. 

 Ulcer in a Cat's Paw. (Cadeac.) 



Fig. 35. 

 Ulcer in a Dog's Paw. (Cadeac.j 



nomena or impair them, may be, for the same reasons as the 

 preceding lesions, effective causes in the development of 

 ulcers. The latter may in fact be met in cardiac and albumi- 

 nuric patients. A peripheric neuritis may favor the appear- 

 ance of sores which have no tendency to heal, but which, on 

 the contrary, become aggravated upon the slightest friction 

 or contact. 



It may therefore be said, in a general way, that every 

 influence that weakens the resistance of the tissues, places 

 them at the mercy of every attack. The cellular elements of 

 which they are composed no longer possess sufficient vitality 

 to repair injury, and the lost substance can not be repro- 

 duced by the process of cicatrization. 



