Partial Excision of the Lateral Cartilage.—­Discarding the somewhat elaborate methods we have just described, there are English operators who removed the necrosed portion only of the cartilage, and do so in what appears at first sight a comparatively rough-and-ready manner.

The apparent roughness is that they do not concern themselves with conserving the coronary cushion, and hesitate but little in cutting portions of it bodily away.  One would imagine that in this case the quarter of the side operated on would be always more or less bare of horn.  Such, however, is not the case.

To perform this operation the animal is again cast and chloroformed.  Some operators, however, use the stocks and dispense with the anaesthetic.  The foot is first well cleaned with soap and water and a stiff brush, and the hair of the coronet over the seat of operation shaved.  Again, too, the horn of the affected quarter is rasped until it yields easily to pressure of the thumb, and the whole of the foot washed in an antiseptic solution.

A probe is now inserted into the opening at the coronet, and the direction of the fistula noted, after which the foot is firmly secured, and an Esmarch bandage and tourniquet applied to the limb.

This done, a triangular or wedge-shaped portion of skin, coronary cushion, and thinned horn is removed with a strong sage-knife or scalpel.

The base of the wedge-shaped portion removed contains the opening of the fistula, and the apex of the wedge should reach to the bottom of the sinus (see Fig. 142).

After the horn is removed and the fistula followed up, it is sometimes found that what we at first thought was its end, it may now be continued in an altogether different direction.

It is again followed up with the probe, and the horn and sensitive structures excised until we are quite certain we have reached its furthest extent.

Attention should next be paid to the cartilage.  Wherever spots of necrosis are found, as indicated by the pea-green colour of the affected parts, they must be carefully excised.  Care should be taken in so doing to carry the line of excision some little distance around the visibly affected parts.  This is done that we may be quite certain nothing at all remains calculated to give rise to further trouble.

It goes without saying that, in addition to the necrosed cartilage, all other diseased and necrotic tissues should also be removed.  The os pedis is occasionally found necrotic just where the cartilage joins it, or it may be that a small portion of the sensitive laminae, by reason of its liver-red or even gray coloration, gives evidence of death of the part.

The former must be well curetted, and the latter cleaned carefully with a scalpel and forceps.

[Illustration:  FIG. 142.—­PARTIAL EXCISION OF THE LATERAL CARTILAGE BY REMOVING A PORTION OF THE CORONARY CUSHION.  The dotted lines show the outline of the wedge-shaped portion of structures to be removed, including skin, coronary cushion, horn, and sensitive laminae. a, The opening of the fistula.]