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CRYSTAL OR SPONGE GOLD. 177

walls of the cavity a surface better calculated to be
retained, than foil in any of its forms; though adhe-
sive foil possesses this advantage to a greater extent

than foil in any other condition. The points and
edges of the crystals are brought in contact with the
walls, and take a firmer hold upon the dentine.
In forming crystal gold into a solid mass, two
principles are operative : cohesion acts upon it as
potentially as upon gold in any other form, and, in
addition, there is the interlacing, or locking, of the
crystals with one another ; so that a more perfect
union of the different portions of which a filling is
composed, is obtained with crystal gold than with

foil. Yet good adhesive foil, when thoroughly
worked in, attains almost the same condition. With
perfect crystal gold, however, some advantages may

be secured, that can not be had with foil. The gold
will be retained in a cavity that will not retain a foil
filling; it is more easily formed into a coherent mass;
cavities can be
it can be built out with more ease ;
filled with it that can not be rilled with foil at all
and a filling of it is susceptible of a better finish, with

the same labor, than a filling of foil.
It is important to keep the gold perfectly free from
moisture, while being introduced and consolidated
for moisture instantly destroys its cohesive property.
And the more complete the exclusion of moisture