Firing has been referred to, in other parts of this work, as an indispensable operation for the cure of lameness, while the actual cautery has also been advocated for the treatment of other forms of disease.
In veterinary practice the term "firing" has by common consent been applied to operations upon the limbs, as distinct from the use of the actual cautery for the destruction of morbid tissues, the arrest of haemorrhage, or the severance of organs (as in castration). In the former case it is employed with two principal objects, namely, the excitation of superficial inflammation outside, but as near as possible to, the seat of injury or abnormal growth, and by its subsequent thickening and contraction of the skin to afford an abiding support unobtainable in any other way. No humane man can witness the operation of burning the living tissues without pain to himself, and it is a matter for congratulation that not only is firing much less practised at the present time than formerly, but the more general use of chloroform by veterinary surgeons has deprived the operation of all unnecessary suffering. Since the necessity of firing is admitted by the best-informed as well as the most humane practitioners, we need not stay to defend the practice, but proceed briefly to describe the methods. Whether the operator proposes to fire in straight lines, on "feathers", "diamonds", "lozenges", or to make punctures with a pointed iron, the preparation will be the same. The part of the limb to be fired should be closely clipped, or the skin will be scorched by the burning hair, and the smoke and charred remains will obstruct the view of the surgeon and prolong the operation.
It is usual to cast the patient with hobbles (Plate LIV), but many men, expert by long practice, succeed in making a fairly good pattern with no greater restraint than that afforded by the twitch, and a front or hind limb held up. Cocaine, injected by several punctures a fewminutes prior to operating, undoubtedly reduces the pain to the animal, and risk to the surgeon who undertakes to fire while the patient is standing. Plain lines about three-quarters of an inch apart probably answer quite as well as the most artistic patterns where the firing is intended to act upon a considerable area, as, for instance, in broken-down ligaments and tendons; but in the case of bony growths, as spavins, side-bones, and splints, punctures may be made with a fine-pointed iron (fig. 511) heated in a fire, or by an aluminium point heated by spirit vapour, as practised in the use of the thermo-cautery. Whether an iron or aluminium instrument is used, the acting surface of the implement should be slightly rounded at the edge, and applied in such a manner as to burn until a dull white appearance of the skin is produced, but avoiding complete division of it, which might result in sloughing and permanent blemish.
Fig;. 510. - Firing Irons.
Plate LIV. HORSE CAST FOR FIRING.
Besides the immediate superficial inflammation produced by the iron, which should be at red heat when taken from the fire, it is claimed for this ancient method of treating lameness, that by causing the skin to thicken and contract it is made to afford permanent support to the part. There are not wanting authorities who deny the claim that firing has the effect of contracting the skin and producing a permanent bandage, and who assert that all the beneficial results the operation confers are obtainable from repeated blisterings. Viewed from the humanitarian aspect, a verdict in favour of firing might be given, in preference to blistering repeatedly, as it is more than likely that a horse suffers as much pain from a blister as from firing, if the latter operation is performed under chloroform. The inflammatory action set up by firing is not more painful than that produced by a severe blister, and as the effects produced by the former can only be obtained by a repetition of the latter there is little to be said against firing on the score of humanity.
The practice of applying a blister immediately to the skin already treated by the iron is not desirable where the lines are drawn close together, but it may be done with advantage in "open" firing. A minimum of two months' rest should be ensured to a fired horse, and as much longer as circumstances permit; the latter part of the time may be spent in a paddock or well-littered yard in preference to a loose-box, where during the first few weeks the patient should be confined. No good object can be obtained by removing the thick and scabby layer which results from the operation, and, unless an early repetition of the blister is required, it should be left to fall away after an under-covering of hair has been produced.
Fit. 511. - Spavin-punch.