186 HORSE, SWINE AND POULTRY DISEASES 



pack the incision with powdered sulphate of zinc and keep the orifice 

 plugged for twenty-four hours. These agents set up a destructive 

 inflammation of the walls. Suppuration follows, and this should 

 now be encouraged by hot fomentations and poultices. The orifice 

 must be kept 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 when the horse is put 

 to work. If treated as above directed, and properly fitted w r ith a good 

 collar after healing, there will not remain any track or trace of the 

 large, unsightly mass. 



FISTULAS. 



The word fistula is applied to any ulcerous lesion upon the ex- 

 ternal surface of the body 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 de- 

 scription 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 which 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, mem- 

 brane and show no disposition to heal. Thev 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 ten- 

 dency 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. 



Causes. Fistulas follow as a result of abscesses, bruises, wounds, 

 or long-continued irritation by the harness. Among the more com- 

 mon causes of fistula of the poll (poll evil) are chafing by the halter 

 or heavy bridle; blows from the butt end of the whip; the horse 



