Causes.—­The cause which we have indicated for canker—­namely, a local specific one, is in all probability the one operating here.  Apparently there is a variance of opinion as to whether the condition is actually canker or not.  We think, however, that the character of the secretion of the affected membranes, the appearance of the growths, the manner in which they react to the hot iron, the comparative absence of pain, and other points of similarity, point to the fact that the two conditions are actually identical.  In other words, the cause is precisely the same, and the only point of difference is the alteration in the point of attack.

Symptoms.—­Like canker, the disease is insidious in onset.  In precisely similar manner the horn, and in this case the skin of the coronet, is underrun.  Later there is the partial shedding and fissuring of the undermined horn and the exuding of the characteristic discharge—­in this case not so watery as that of canker.  The caseous material of canker is also present, as is a disposition to hypertrophy of the exposed sensitive structures.  What horn is left becomes rough and irregularly fissured, and has been likened by some observers to deeply-wrinkled bark of an old tree.  A peculiar characteristic of this condition is the state of the ergots and chestnuts.  Here the keratogenous membrane participates in the diseased process, and their horn becomes dry and brittle, and readily splits into small fibrous bundles very similar to the fibroid growth described in canker.  These excrescences are easily separated from the sensitive structures beneath, and the exposed surface is seen to be more or less moist, or even exhibiting a slight oozing of blood.

Again, as in canker, the deeper layers of the sensitive structures appear to be normal, the horn-secreting layers being the only ones affected.  According to Malcolm, the disease is in its nature equally as inveterate as canker, but it is easier to treat, on account of its more exposed position.

Treatment.—­This is exactly that as described for canker.

[Illustration:  FIG. 137.—­SPECIFIC CORONITIS OF ALL FOUR FEET.]

[Illustration:  FIG. 138.—­OFF FORE-FOOT AFFECTED WITH SPECIFIC CORONITIS.]

Recorded Case.—­The subject of this case was a young black cart gelding.  The disease is reported as having begun as thrush, and then extended to the coronet.  When I saw him he had been in a similar condition to that depicted in Fig. 137 for, it was said, two or three months, the driver of the horse meanwhile endeavouring to effect a cure by some potent drug of his own.  The animal was in good condition, but walked with difficulty owing to the pain.  The coronary bands were swollen to two or three times their natural size, and this caused the hair immediately above to curl upwards.  Just below the coronary bands there was a line of separation between them and the wall.  They themselves were