ABSCESSES AND FISTULAS. 477 



hot fomentations and poultices. The orifice must be kejDt open, and 

 should it be disposed to heal we must again introduce some of the 

 agents above described. A favored treatment with many, and it is 

 probably the best, is to plunge a red-hot iron to the bottom of the 

 incision and thoroughly sear all parts of the walls of the abscess. 

 This is to be repeated after the first slough has taken place, if the 

 walls remain thickened and indurated. 



It is useless to waste time with fomentations, poultices, or blisters 

 in the treatment of cold abscesses, since, though apparently removed 

 by such methods, they almost invariably return wdien the horse is put 

 to work. Extirpation by the knife is not practicable, as the walls of 

 the tumor are not sufficiently defined. If treated as above directed, 

 and properly fitted with a good collar after healing, there will not 

 remain any track or trace of the large, unsightly mass. 



FISTULAS. 



Definition. — The word fistula is applied to any ulcerous lesion upon 

 the external surface of the bod}^ which is connected by ducts, or 

 passages, with some internal cavity. Because of this particular 

 formation the term fistulous tract is often used synonymously with 

 the word fistula. Fistulas may exist in any part of the body, but the 

 name has come to be commonly accepted as applicable only to such 

 lesions when found upon the withers. Poll evil is a fistula upon the 

 poll, and in no sense differs from fistulous withers except in location. 

 The description of fistula will apply, then, in the main, to poll evil 

 equally well. Quittor presents the characteristic tubular passages of 

 a fistula and may therefore be considered and treated as fistula of the 

 foot. Fistulous passages may also be developed upon the sides of the 

 face, through wdiich saliva is discharged instead of flowing into the 

 mouth, and are called salivary fistulas. A dental fistula may arise 

 from the necrosis of the root of a tooth. Again, a fistula is sometimes 

 noted at the umbilicus associated with hernia, and recto- vaginal 

 fistulas have been developed in mares, following difficult parturition. 

 Fistulas may arise from wounds of glandular organs or their ducts, 

 and thus we have the so-called mammary, or lachrymal, fistulas. 



Fistulous tracts are lined with a false, or adventitious, membrane 

 and show no disposition to heal. They constantly afford means of 

 exit to the pus or ichorous material discharged by the unhealthy 

 parts below. They are particularly liable to develop at the withers 

 or poll because of the exposed positions which these parts occupy, 

 and, having once become located there, they usually assert a tend- 

 ency to further extension, because the vertical and laminated forma- 

 tion of the muscles and tendons of these parts allows the forces of 

 gravitation to assist the pus in gaining the deeper-lying structures 

 and also favors its retention among them. 



