238 THE HORSE. 



WOUNDS OF THE SKIN. 



F'istulse. The word fistula is properly applied to sinuous pipes ot 

 ducts leading from cavities to the surface of the body, through which a 

 discharge is constantly taking place. They are lined by a false or 

 adventitious membrane, and show no disposition to heal. Fistulae 

 may then exist at any part, but the name has come to be com- 

 monly accepted as applicable only to such discharges taking place 

 from the withers, and we shall refer to this location when using the 

 term. 



Poll evil is a fistula upon the poll, and in no sense differs from fistu- 

 lous withers except as to location. The description of fistula will apply 

 then, in the main, to poll evil as well. Fistulas are particularly liable 

 to occur at either of these locations from the disposition of the muscles 

 and tendinous expansions, which favor the burrowing of pus and its 

 retention. Fistulae follow as a result of abscesses, bruises, wounds, or 

 long continued irritation by the harness. Among the more common 

 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 striking his 

 head against the hayrack, beams of the ceiling, low doors, etc. Fistu- 

 lous withers are seen mostly in those horses that have thick necks as 

 well as those that are very high in the wither; or, among saddle 

 horses, those that are very low on the withers, the saddle here riding 

 forward and bruising the parts. They are often caused by bad-fitting 

 collars or saddles, by direct injuries from blows, and from the horse roll- 

 ing upon rough or sharp stones. In either of these locations, ulcers of 

 the skin, or simple abscesses, if not properly and punctually treated 

 may become festulse. The pus burrows and finds lodgment deep 

 down between the muscles, and only escapes when the sinus be- 

 comes surcharged or during motion of the parts, when the matter is 

 squeezed out. 



Symptoms. These of course will vary according to the progress 

 made by the fistula. Following an injury we may often notice sore- 

 ness or stiffness of the front legs, and upon careful examination of 

 the withers we will see small tortuous lines running from the point 

 of irritation downward and backward over the region of the shoul- 

 der. These are superficial lymphatics, and are swollen and painful 

 to the touch. In a day or two a swelling is noticed on one or both 

 sides of the dorsal vertebrae, which are hot and painful and rapidly en- 



