60 THE DISEASES OF THE HORSE. 



that is, have an external or internal opening only, or 

 both. The canal may be short or a foot or more in length. 

 Fistulae (pleural of fistula) are caused by diseased bone, 

 cartilage, tendon, &c, and are hard to heal. 



Remedy. — Before pus is formed, reduce inflammation 

 with cold water to the part; then iodine and a purge; 

 do not puncture. After pus is formed, enlarge the canal 

 with a knife ; pass seton or otherwise provide dependent 

 opening. Kemove diseased bone or other irritant. En- 

 courage healing of wound from below. Where the kuife 

 is unsuitable, inject saturated solution of corrosive subli- 

 mate, or sulphate of copper or zinc. Where milder treat- 

 ment fails, slough out ulcerating surfaces and secreting 

 walls with corrosive sublimate or arsenic plug. Dress with 

 carbolic acid or other antiseptic. (For doses, see pages 13 

 to 29.) 



POLL-EVIL 



Is a fistulous ulcer at the poll of the neck, near the 

 ears. From a simple swelling it develops into a tumor, from 

 a tumor into an abscess, and from an abscess into deep- 

 seated, chasm-like ulcers. It is caused by tight bearing- 



Fig. 11. Poll-Evil; ready for operation. 



reins, blows, bruises, pressure, friction, &c. A stiff and 

 hard halter or other head-gear or collar may cause fric- 



