The whole of the foot must then be thoroughly cleansed, and rendered as nearly aseptic as possible.  The use of warm water, soap, and a stiff brush is the readiest means of removing the surface dirt.  Afterwards the foot should be soaked for some time in a reliable antiseptic solution, a 1 in 1,000 solution of perchloride of mercury being the most suitable.  When removed from the solution the foot must be packed round with wool or tow impregnated with corrosive sublimate, and then bandaged, the whole afterwards wrapped in a thick cloth, or protected with a boot.

On the following day the animal is brought out and cast, and the foot desired to be operated on firmly secured, after the manner described on p. 81.  The bandages and sublimate pads are then removed, and the skin of the coronet over the seat of operation shaved of hair.  An Esmarch rubber bandage is next run up the limb, and the tourniquet applied, thus rendering the operation a nearly bloodless one.

This done, the animal is chloroformed, and an antiseptic douche played over the foot.

So far, the steps in the operation are common to all methods.  There are now, however, three slightly differing modes of extirpating the cartilage, which modes vary simply according to the structures severed by the knife.

First Method.—­This is the oldest method of the three, and consists in making (1) a horizontal incision through the sensitive laminae along the lower border of the cartilage, and (2) a vertical incision through the skin of the coronet, the coronary cushion, and a portion of the sensitive laminae (see Fig. 139).

The flaps (Fig. 139, a, a) are now held back by tenaculae, and the whole of the cartilage, or only the necrosed portion, carefully excised by means of right- and left-handed sage-knives.  Fistulous openings in either of the flaps a, a must now be carefully curetted and dressed, and the flaps allowed to fall into position.  They are then sutured with carbolized gut, and the wound finally dressed as to be described later (p. 357).

[Illustration:  FIG. 139.—­EXCISION OF THE LATERAL CARTILAGE (OLD METHOD).  The wall covering the lateral cartilage first thinned and stripped off; the two flaps (a, a) of skin and the coronary cushion made by the vertical incision turned back. a, The operation flaps; b, the exposed cartilage; c, the sensitive laminae; d, the coronary cushion.]

Second Method (after Holler and Frick[A]).—­These operators deem it wise to leave untouched the skin of the coronet and the coronary cushion.  They therefore make their first incision along the lower border of the coronary cushion (see Fig. 140), afterwards exposing the lower half of the cartilage by removing a half-moon-shaped portion of the thinned horn and underlying sensitive laminae (see Fig. 140, b).

[Footnote A:  Two cases of quittor successfully treated by this method are reported by R. Paine, M.R.C.V.S., in the Journal of Comparative Pathology and Therapeutics, vol. xv., p. 81.]