320 DISEASES OF THE HORSE'S FOOT 



this purpose it is best used as a dry powder. Under this 

 dressing any remaining spot of canker is readily detected 

 by the wet condition of the calomel when the shoe is 

 removed the next day. In dealing with such a spot, a very 

 good plan, after all apparently diseased tissue has been 

 excised, is to touch the cankered part with solid nitrate of 

 silver, or a feather dipped in one of the strong mineral 

 acids, and then reapply calomel over the surface. The 

 result of this treatment is frequently very gratifying. 



' In successful treatment the shoe must be removed each 

 time — an adjustable plate will not do, as no man can 

 thoroughly pare and examine a foot with the shoe on, and 

 imperfect dressings are worse than useless. Indeed, it is 

 better not to pare or thin the horn at all, than to imper- 

 fectly pare, since canker, if undestroyed, develops far more 

 rapidly under thin horn than under thick. 



' In conclusion, I would again urge the necessity, at the 

 very first operation, when the horse is down, of removing 

 every single particle of the diseased tissue, either by excision 

 or effectual cauterization, but at the same time taking very 

 great care to guard against the latter being too destructive. 

 The cautery should be laid aside as soon as the tissue 

 cauterized ceases to burn white. The moment at which the 

 canker has thus been eradicted without destroying sound 

 tissue is indicated by the appearance of healthy horn, by 

 the intimate union of that with the secreting surface, and 

 by the healthy aspect of the exuded blood when paring has 

 been carried to the quick. 



■ Should subjacent healthy structures be destroyed during 

 the process, that is shown by the production of a raw sore, 

 or of a sore to which a "sit-fast," coextensive to the injury, 

 is firmly attached. This seriously retards recovery. The 

 secreting surface having been destroyed, no new horn can 

 be produced directly from the part, and a new secreting 

 surface and new horn have now to grow inwards from the 

 surrounding undestroyed tissue, and that is a slow process. 

 At the same time, on the principle of choosing the least of 

 two evils, practical experience teaches that it is better to 



