The best plan is to have the water with just the chill off, and then add salt in the proportion of as much as will lay upon a sixpence to half a pint of water. If you wish the plaster to set quicker than under these circumstances it would do, add to it before mixing a small portion of rouge. This will make it set so quickly, and so strongly, that increased care and watchfulness will be required with regard to the proper time for removal from the mouth. Everything being now ready, the plaster is mixed in the ordinary manner to the consistence of thick cream, care of course being taken to break up all lumps in it during mixing; a sufficient quantity is then placed in or upon the impression-plate, and the whole steadily introduced into the mouth and held firmly in its place, the precaution being adopted at the moment of putting the plate in position to incline the patient's head forward, so as not only to get a good overlap above the anterior margin of the cleft, but also to lessen the liability of any plaster running down backwards and causing retching.

Now is the time to test the patient's confidence in the operator. If there is any evidence of restlessness or nervousness, divert the attention by some remark, or by examining the plaster remaining in the bowl in order to ascertain the precise moment for removing the impression from the mouth,-by these or similar means to make the

time (which should only occupy about a minute and a half) appear less, and save any disagreeable consequences either to yourself or the subject of your operations. To those inexperienced in these matters all this instruction may appear superfluous, but its neglect will assuredly upon many occasions lead to a decidedly "embarrassing situation."

When the remains of the unused plaster in the bowl will break asunder and leave a clean, sharp fracture, then it is time to remove the impression from the mouth. If at the first it cannot be disengaged easily, then at once and without any hesitation use sufficient force to detach it, bearing in mind that at such a time every second's delay increases the difficulty. Under ordinary circumstances it will break away in the line of the cleft. This need occasion no alarm only desire your patient to sit perfectly still and keep the mouth well open; you can then without any anxiety or hurry push the part which remains above the margin of the palate carefully backwards to the widest part of the opening, and, firmly seizing it with a pair of long tweezers (as shown in fig. 22) withdraw it.

The fractured parts, when put carefully together, will be found quite as efficient for use as if no breakage had taken place, especially if, instead of using resin and wax cement, they are united

with liquid silex, as recommended in the British Journal of Dental Science for June, 1868,* by which means any increase of bulk is avoided.

FIG. 22. The entire length of these Tweezers is eleven inches with the handle.†

The impression, being thus perfect, must be carefully washed over with a solution of soap (brown Windsor is the best for the purpose), and the model made in three portions, as shown in the accompanying engraving (fig. 23). We now eturn to the more commonplace operations of the work-room, and further minute particulars would only become tedious and unnecessary.

The model being ready for use, the artificial velum must be set up in gutta percha, having the precise shape which it will possess in its finished form. Here instruction on our part is useless, as the formation of the palate-piece will depend entirely on the characteristics of the case and the ingenuity of the operator. The gutta percha should be of the best description, and the

* "Liquid Silex." By James Oakley Coles.

† Made by Messrs. Ash and Sons, Broad Street Golden Square.

model prepared with soapstone, to prevent any adhesion to its surface. When this is worked up to a satisfactory state, the casting of the plaster moulds can be proceeded with. For an ordinary

case the best form is that shown in the engraving (fig. 24, page 72). These, however, admit of very many modifications, according to the shape of the velum, in preparation. The plaster castings, when complete, must be duplicated in type metal, the best metal obtainable and the finest castingsand only being used. Great care must be taken

here, as any imperfection in the metallic moulds will be communicated to the surface of the rubber during vulcanizing, and can only be remedied by clipping and paring, which gives a very unsightly appearance to the finished work. When the castings are complete, and the surfaces well polished with pumice powder and water by means of a stick of dog-wood, they should fit together accurately; if they do not, there is no alternative but to commence de novo till you arrive at a satisfactory result.

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The accompanying engraving (fig. 24) shows the castings separated, also the metallic pin fixed in the base for producing the hole in the velum by which it is attached to the hard rubber front piece. Any error with this will be found to upset the entire arrangement. The greatest care must therefore be used in getting it into a good position, according to the shape of the cleft and mouth. The moulds having been well soaped to prevent adhesion, and made warm-not hot-the next step is to pack them with elastic rubber. This is very easily accomplished: the two sidepieces, being adjusted to the base, are kept firmly in position by an iron clamp, and the rubber packed in from above. When there appears sufficient, the top is put on, and the whole screwed tightly together, being put on a hot plate for a few minutes to soften the rubber. The casts are then taken