That fissures in the wall are undoubtedly a cause has been placed on record by the late Professor Walley, who noticed the appearance of these horny growths following upon the operation of grooving the wall.[A]

[Footnote A:  Journal of Comparative Pathology and Therapeutics, vol. iii, p. 170.]

This gentleman had a large Clydesdale horse under his care for a bad sand-crack in front of the near hind-foot, and, as the lameness was extreme, he adopted his usual method of treatment—­viz., rest, fomentations, poulticing, and the making of the V-shaped section through the wall, and subsequently the application of an appropriate bar shoe to the foot, and repeated blisters to the coronet.  In a short time the lameness passed off, and the horse was put to work.  A few days later the animal met with an accident, and was killed.

On examining a section of the hoof it was found that a vertical horny ridge corresponding to the external fissure had been formed on the internal surface of the wall, and that a well-marked cicatrix extended upwards through the structure of the hoof at the part forming the cutigeral groove; furthermore, a similar ingrowth had been taking place in the line of the oblique incisions made for the relief of the sand-crack.

This case has an important bearing on the operation of grooving the wall, which operation we have several times in this work advocated for the relief of other diseases.  It teaches us that the incisions should not be carried so completely through the horn as to interfere with and irritate the sensitive laminae, and so set up the chronic inflammatory condition leading to hypertrophy of the horn.

From the position on the os pedis of the indentation made in it by the keraphyllocele (see Fig. 133) it has been argued that pressure of the toe-clip is a cause of the new growth.  This, we should say, cannot be a very strong factor in the causation, for, while we admit that the continual pressure of the clip, and the heavy hammering that sometimes fits it into position, is likely to set up a chronic inflammatory condition of the sensitive laminae in that region, we must still point out that the rarity of keraphyllocele, as compared with the fact that clips are on every shoe, does not allow of the argument carrying any great weight.

Symptoms.—­Except under certain conditions this defect is difficult of detection.  As a rule, lameness is not produced by it.  In making that statement we are led largely by the conclusion arrived at by Professor Walley.  This observer noted the fact that ingrowths of horn such as we are describing nearly always take place in false quarter, or after a sand-crack has been repaired, and that they commonly occur after the operation of grooving the wall in the manner we have just shown.

Now, we know that quite often under these circumstances the horse goes perfectly sound.  Thus, while we know that in all probability keraphyllocele is in existence, we have ocular demonstration that the animal is quite unaffected by it.