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158 THE MICRO-ORGANISMS OF THE HUMAN MOUTH.

light portions, finally, var^' exceedingly in respect of their
outlines, according to the form in which the carious limits are
extended, being radiated, kidney-shaped, etc." (Wedl.)
A true picture of transparency can be obtained only where
softening and pigmentation of the dentine have not yet taken
place ; that is to say, where there is as yet no decay. The trans-
parent portion here forms a cone whose apex points toward the
Fig. 61.

Begixsixg Decay ok Enamel mith Thansi'auext Coxe or Dextixe.
I'nder weiik power.

pulp and whose sides run parallel with the dentinal tubules. In
most cases the transverse sections of these cones are, as far as
my observations go, bounded by two opaque stripes (Fig. 61, a).
Uuderthe microscope, the dentinal tubules within these stripes
are seen to be filled with irres^ular, anjiuhir granules or oblong
particles,
I have not been al)le to discover analogous plienomena in