The passing of probes into the duct from its lower aperture is useful in removing trifling obstructions caused by concretion of deteriorated mucus, or slight thickening of the lining membrane, and in chronic dilatation of the sac with probable contraction of the duct. But, at the same time, it is an operation requiring much dexterity, and which ought not to be attempted till after much practice on the dead body. The first introduction of the instrument is always the most difficult, from obstruction by a valvular projection of the membrane at the lower orifice, the use of which in the healthy state of the parts must be apparent. Destruction of it renders after-introduction of instruments much more easy. But the preferable practice is making an opening into the sac, and then introducing instruments from the upper orifice of the duct; more especially in cases where the swelling and pain are considerable. The instruments employed for dilatation of the passage are tubes and styles. The tubes are made either of silver or gold, of equal calibre throughout, and of the same length as the passage. For some time after their introduction they cause much irritation; this gradually diminishes, and the wound heals over them. But, according to my experience, the effects are not satisfactory. The irritation which they at first occasion generally subsides, but abscess again occurs, with much swelling, and it becomes necessary to remove the foreign body. Again, the tube sometimes becomes obstructed by thickening and concretion of the discharge, and then, when it is necessary to remove it, the process is found to be by no means an easy one; a free incision is required; a screw must be fastened into the tube, or, when that cannot be accomplished, the foreign body must be laid firmly hold of with strong forceps; altogether the extraction is very painful, and often extremely tedious. In short, the practice of introducing tubes does not appear to be founded on sound surgical principles.