This term signifies a wound on the poll, or that part of the neck immediately behind the ears. It usually consists of one or more sore places in the skin communicating by pipes (sinuses) with a cavity seated more or less deep down in the tissues, sometimes extending to the bones, the whole constituting what is termed a "fistula".
It is caused by an injury, frequently inflicted by the horse striking his head against some hard substance, as a low beam, ceiling, or doorway, or against the floor or wall in the act of rolling, or by a violent blow with any hard substance, as a whip-stock, fork-handle, etc, bruising the skin and underlying structures so as to interfere with the circulation of the part. It has also been caused by stretching these parts by the injudicious use of the bearing-rein, and by badly-fitting or heavy bridles chafing the poll.
The symptoms at first depend a good deal upon the severity of the injury. If this be slight we may only find a small swelling on the nape of the neck, which soon passes away again after a short period of rest, even without any treatment at all. At others there is a small hard knot left, which upon the slightest injury - and with such a swelling injuries are easily inflicted - rapidly enlarges to the size of a cricket ball or more. This swelling is very painful to the touch, and causes the animal to carry his head in a stiff manner, with the nose slightly poked forward and upwards to relieve the tension of the muscle at the back of the neck. After a time - usually from one to three weeks - there appears a soft place on the swelling, which shows us that the part has gathered and formed matter (pus), which has found its way to the surface (pointed). If not opened it will soon burst through the skin and discharge a thin yellowish-red matter, which after a few hours changes to a yellowish-white colour.
When the matter is allowed to remain pent up in the tissues, it will burrow between the muscles in all directions, and occasion a wound with several pipes (sinuses), which proves, as a rule, a very formidable one to cure, particularly if the pax-wax or great ligament of the neck, or the bones below, become involved. The matter (pus) may run down the neck between the muscles - even as low as the shoulders, as we once had occasion to observe; or the neck bones (cervical vertebrae) may become diseased, giving rise to death (necrosis) of the bones, or to their permanent enlargement and union with each other (anchylosis), producing a chronic stiff neck; or the ulceration may extend even to the spinal canal, causing pressure on the cord and consequent paralysis, or epileptic seizures, or sudden death. One or both sides of the neck may be affected.
In the early stages, when the swelling is hot and tender, the treatment should consist of cold applications to the part, such as cold douches, which may be applied by fixing a hose-pipe to a tap, or by syringing two or three buckets of cold water over the poll three or four times daily with a garden syringe. Then apply linen cloths soaked in a solution of sal ammoniac and saltpetre in water. During this time the animal should be kept on bran mashes or other light food, and receive a dose of physic, to be followed by green foods in summer or roots in winter. Should this line of treatment not be successful in allaying the inflammation and reducing the swelling, we may be sure that it means to gather, particularly if it becomes more painful to the touch. As soon as we are satisfied that it is gathering (forming an abscess), we should encourage the process as much as possible, for the sooner we can get the matter to the surface the better. This is best effected by the application of hot-water fomentations and stimulating lotions. If the swelling does not seem inclined to "point" quickly, a smart blister to the most prominent part of it will usually hasten on the process. Directly the abscess "points" we should lose no time in opening it, and this should be done at the lowest part of the cavity, so that a natural drainage may be obtained and retention of the matter avoided. If this can only be properly done at this stage, we shall find very little difficulty in healing the breach, - i.e. when the great ligament of the neck and the bones are not affected.
If, however, as is usually the case, the wound is neglected at this stage, the matter (pus) begins to burrow between the muscles, forming pipes (sinuses) in various directions; these must be bottomed and laid freely open. There are various means of doing this. Some prefer the knife, but this, even in skilful hands, is not always successful, because the pipes run in such intricate and awkward directions that it is extremely difficult to follow them; others, again, use caustics, and destroy the pipes and the surrounding structures. There are several of these agents; one of the oldest, best, and perhaps the commonest, is corrosive sublimate. Arsenic is often used, but it requires great care; and even with the most discreet it will sometimes act far beyond their expectations, and damage or destroy neighbouring structures, which adds to the trouble of the case by causing delay, and may also prevent recovery. If the cautery has been successful, all that is required after is cleanliness and the application of some astringent and antiseptic lotion, as carbolic acid. Occasionally, however, the healing process "hangs fire", as the old practitioners used to say, and then a stimulating lotion to encourage granulation is required.
Another line of treatment is to pass a piece of tape (seton) besmeared with some digestive ointment to the very bottom of the wound and bring it out again at a lower level. This is a very common and sometimes successful practice when both sides of the neck are affected, the tape being passed from one side to the other and allowed to remain until the wound has healed, leaving only the canal through which the tape passes, when it may be removed and the canal allowed to heal up.
When either the great ligament of the neck or the bone is diseased, it becomes a very formidable case, because both these structures have a slow circulation and little reparative material is brought to them. Then again, they are so deeply situated that it is difficult to get at them to cut away any diseased part. When, therefore, either of these structures is involved, we may be sure it will take a long time - even months - before a cure can be effected. Finally, we may say there is no hard-and-fast line of treatment in these cases, but each has to be taken on its own merits and treatment adopted accordingly.
It will be readily seen from the foregoing that poll evil may be prevented by having the stable doors and ceiling high enough to prevent the horse striking the top of its head, also having light and well-fitting bridles, and a kindly-disposed and attentive groom or horse-keeper, so that should any chafing occur he would give it immediate attention, and so ward off a most troublesome disease.