PRINCIPLES OF VETERINARY SURGERY 375 



The inflammation in fistulous tracts is always spurious and 

 must therefore be transformed into an acute, free process. 

 For this purpose three principal expedients are employed, 

 viz., caustics, actual cautery, and setons. Among the caustics 

 preference is given to sulphate of copper, sulphate of zinc, 

 solutions of the three sulphates, nitrate of silver, chloride of 

 zinc, permanganate of potash, resinate of copper, tincture of 

 iodine and five per cent solution of carbolic acid. 



When the fistulous tracts are very large and have a 

 pendent cul-de-sac, the seton allows the pus to flow outvvard 

 and by irritating the tract transforms the chronic inflamma- 

 tion into an acute process. It is sometime necessary to 

 augment this effect by applying some irritating substance to 

 the seton. For this purpose blisters, oil of turpentine, etc., 

 are frequently employed. When the tract is limited in ex- 

 tent the cautery gives positive results. 



These directions apply only to idiopathic fistula. For 

 symptomatic fistula the therapy is quite different. Sympto- 

 matic fistulse are. manifestations of a deep lesion (necrosis or 

 caries) and as a consequence the tract will only dry up after 

 the purulent center has been removed. The preceding direc- 

 tions are therefore insufficient as a guide for the cure of the 

 symptomatic variety. Recourse must be had to surgical in- 

 tervention. The necrotic center must be extirpated, and 

 provisions must be made to prevent the pus from lodging in 

 the tissues during the healing process. 



These general data require completion by the study of 

 special methods of treatment employed for the various 

 fistulce (See Vol. III). 



ERYSIPELAS. 



During the last few years the word "erysipelas" has been 

 employed by veterinarians to describe a number of surgical 

 complications which have more or less remote analogies to 



