There is a canal below the inner corner of the eye through which the superfluous tears flow into the cavity of the nose. When the tears are secreted too rapidly to be thus carried away, they run down the cheek, and they do so when this canal is obstructed. An obstruction may be caused in this canal by inflammation of its lining membrane, or by the introduction of a portion of hardened mucus into it When an obstruction occurs, the upper part of the canal is evidently distended with the fluid. There is a soft tumour below the inner angle of the eye. This for a considerable time alternately appears and disappears, or the fluid may often be pressed down towards the nose, or upwards into the eye, by a little careful management with the finger. At length, from frequent distension, the membrane of the canal becomes diseased; it is ruptured, and an ulcer is seen below the eye. This is the fistula lacrymalis.

The ulcer, being once formed, will never be healed; it is the passage for the tears which nature has contrived, the true canal having been obstructed. The old canal can never be re-opened; we have no instruments sufficiently delicate for the purpose; or, if we had, we could not give the dog patience enough to wear them.

The practitioner, therefore, should confess at once the hopelessness of the case, and limit his directions to simple cleanliness.