with six or eight sides, and cut on each alternate side. In the use of these instruments the drill-ring is almost indispensable. This is a ring used on the middle or index finger, with a socket attached, in which rests the end of the handle of the instrument. (Fig. 16.) The drill is rotated commonly with the thumb and fingers.

Drill-stocks of various forms have been invented, with the view of increasing the motion of the drill, of augmenting its power, and especially of bringing it to bear upon points inaccessible to the straight in

strument.

The use of the burs and drills by the hand, and by means of the various drill-stocks, has been almost wholly superseded by the introduction and use of the dental engine.

This appliance, in a far less perfect form than now, was introduced to the dental profession about the year 1870.

Mr. Green, of Michigan, first introduced the pneumatic engine; succeeding this, was that denominated the "Morrison Engine." Within a short time after this, the suspension engine was devised and constructed by Dr. W. S. Elliott.

This engine possesses some excellent qualities. Its steadiness of motion, freedom from tremor or backlash, and the facility of use, are qualities that make it very valuable in these respects. When the large dress

ing burs or polishing cones are being used it is superior to any other.

The illustration on page 107 (Fig. 17) gives a correct idea of the machine.

Various other modifications of dental engines have from time to time been presented, a description of which is unnecessary here. That improved by, and bearing the name of S. S. White, is at present very popular; it has now the most prominent position before the profession; other modifications, however, are highly esteemed by many. It is well represented by the illustration on page 108 (Fig. 18).

This engine certainly possesses many desirable qualities. The facility of movement and adaptation

afforded by the flexible cable, and the hand-piece, seem to be about all that can be desired. The mode of attachment to and retention of the drills and other ac

factured of the best steel, and wrought with the greatest care. After having been forged as near the proper size as possible, the bulb is shaped by dressing with a fine file, or, which is better, by turning in a lathe,

FIG. 9.

those made by the latter method being superior, and cutting much more smoothly; they do not catch and jar as do those of less regular form. After the bulb is formed, it is cut with a sharp-edged file.

FIG. 10.

Of these drills, Fig. 9 represents a bur of a spherical form. Fig. 10 is cone-shaped, which may have various degrees of bevel, terminating in a sharp point. Fig. 11 is of a cylindrical form, cut upon the sides and end.

FIG. 11.

Fig. 12 is in the form of a wheel, cut upon the edge only, or upon both the edge and the end. The cutting upon all of these should be very regular and uniform. This should be made by machinery, though it is