An abscess may first appear as a hot, painful swelling. If superficial, the skin feels tense and the contents fluctuate when pressed on. Later the fever subsides and no pain may occur when the abscess is pressed upon. Deep abscess may not fluctuate. _The treatment_ consists in converting the abscess into an open wound whenever possible. The incision should extend to the lowest part of the wall, so as to insure complete drainage. A cold abscess in the shoulder region may become lined by a layer of tissue that retards healing. In order to hasten the healing process, it may be necessary to remove this. Until granulation is well advanced, the abscess cavity should be irrigated daily with a one per cent water solution of liquor cresolis compositus, or a one to two thousand water solution of corrosive sublimate. The surface of the skin in the region of the abscess should be kept clean. [Illustration: FIG. 60.--Fistula of the withers, showing the effect of using caustics carelessly.] FISTULOUS WITHERS AND POLL EVIL.--These terms are applied to swellings, blood tumors, abscesses and pus fistulae that may be present in the region of the poll and withers (Fig. 60). Pus fistula is the characteristic lesion present, and it is the result of a suppurative inflammation of the tissues in the region. The abscess cavity or cavities are usually deep, and may involve the ligaments and vertebrae. Bruises or contusions are the most _common causes_. The prominence of these regions predisposes them to injury in the stable, or when rolling on rough or stony ground. Bites and bruises to the withers resulting from other horses taking hold of the region with the teeth, or striking the part against a hard surface, are frequent causes. _The treatment_ is both preventive and surgical. All possible causes should be investigated. This is of special importance on premises where several horses develop fistulous withers and poll evil. If the cause then becomes known, it should be removed. _The surgical treatment_ consists in opening up the different abscess cavities, providing complete drainage for the pus and destroying the tissue that lines the walls of the cavities. Horses that are prone to rub the region should be prevented from doing this, as such irritation retards healing. Autogenous bacterins should be used in addition to the surgical treatment. A pus fistula should heal from the bottom, and if the opening becomes closed, drainage should be re-established. The daily treatment is the same as recommended for abscesses. Excessive cutting and destruction of the tissues with caustic preparations result in scarring and deformity of the part. Such radical lines of treatment should be discouraged. We should not delay the surgical treatment of abscesses in the regions of the poll and withers. QUESTIONS 1. Name and describe the different forms of inflammation. 2. Give the causes and treatment of inflammation.