that have once been operated on, will, at intervals, ever after during the life of the horse, need the hand of the surgeon. If caries, however, is neglected, and proceeds to the last stage, cure is all but hopeless. During the death of a tooth, the symptoms are continuous. In caries, there are intermissions, seasons of uncertain duration, during which the horse appears to be free from suffering; but the effects, if not so rapid in their development, are more frequently fatal in their termination. When a tooth has lost its vitality, it becomes a foreign body, which Nature, in time, will cast out. The retention irritates the surrounding structures, but the irritation may in part be regarded as a restorative process. When caries takes place, a portion only dies, but that portion has all the injurious effect which could be attributed to the former case, and even more, for the remaining vitality in the unaffected part of the tooth, prevents Nature from resorting to that process by which she would otherwise cast off the dead matter. In consequence of this, a foreign substance is retained for a longer period, and at the same time disease is progressing. Here, therefore, is an additional cause at work, and hence the excess of effect. The arteries which nourish the pulp, and the crusta petrosa, proceed from the vessels which nurture the bone, and supply the mucous membrane of the sinuses with the means of secretion. The same, likewise, may be stated of the nerves going to the tooth, and though through these last the constitution is affected, it is mainly through the agency of the blood vessels, that the sinuses become diseased. Hence the necessity for decision, and the need of judgment, in the application of the remedy. To enforce the foregoing remarks, and convey to the reader a slight idea of the consequences which ensue from a carious tooth, the accompanying wood-cut is introduced. The specimen selected for illustration, does not exhibit a rare or extraordinary proof of the results of this species of disease. [Illustration]