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THE MICRO-ORGANISMS OF DENTAL DECAY. 215 ;

reported in L'Odontologk, although not yet concluded, appear
to be deserving of more notice.
The investigators named have examined eighteen decayed
teeth, in all which they found four different kinds of bacteria
a tifth kind they met with eight times, and a sixth five times.
1. The first kind met with is a short, thick bacillus, not
forming chains. It has a length of 1.5«, and is almost as thick
as it is long. In puncture-cultures, in gelatine, it grows tolerably
rapidly, forming a white trail, and begins to liquefy the gelatine
at the end of the third or fourth day, turning it white and
opaque. In plate-cultures it forms small, slightly prominent
colonies, w^iich having attained a diameter of two to three
millimeters spread out in the liquefied gelatine.
2. The second kind is a bacillus 3.0// long and about one-half
as thick, slightly constricted in the middle. Its cultures are
similar to those of the preceding, except that its colonies spread
out more upon the surface of the gelatine before liquefying it.
3. The third kind is a bacillus quite similar to the preceding,
showing, however, no constriction. It is S(piare at the ends, and
forms quite long chains, particularly in liquid media. It does
not liquefy the gelatine, but slightly softens it.
4. The fourth kind is a very small, thin bacillus, almost as
thick as long, so that it might at first be mistaken for a coccus.
It forms a white trail in the gelatine, which it speedily turns
yellow and then liquefies.
5. The fifth kind, found but eight times, is a bacillus with
rounded ends, which forms at first a white trail in the gelatine
and then liquefies and clouds it.
6. The sixth micro-organism, found but five times, is a very
large coccus. It was found only in advanced stages of decay,
where the canaliculi were already considerably dilated, it being
too large to enter the sound tubuli.
It forms trails in the gelatine, which it does not liquefy, and
to which it lends a whitish aspect.
In a memoir, soon to be published, Galippe and Vignal
promise to present in detail the characters of the cultures above
mentioned.