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84 EMIUIYOLOGY OF THE DENTAL TISSUES.

eiiamol cells (Fij;. 68). These, given (nit from tli(> cell continually,
form the cnaniel rods. One rod is separated tVoni anotlici' hy a |n-oto-
j)lasnuc cenieut substance.
Dr. Graf Spee says that whcii the tissue is j)roj)erly ])repared—and
he lays great stress on this point—at the time of the formation of the
enamel, the globules are always to be found. Their entire absence at
„ „„ earlier stap-es is an indication that
^
Fig. 72.
these globules are an enamel sub-
stance. He gives to them the name
'* enamel drops," and says he saw
these " enamel drops," when enamel
is to be formed, appear only in the
half of the enamel cells wdiich rests
on tiic dentin; afterward they were
[J
to be seen farther up in the cell, but
not quite to the region of its nucleus.
Many of them were so small as to be
scarcely measurable, and they are al-
ways spherical. Great numbers of
Section of (leveinpiM t .1, of calf at birth, ^\^^,^ ^^^ collected at the periphery,
showinj; tirst-foriiiiii;; layer i)f enamel. The l i j 7
,
globules of caico-giobuiin are seen arranged and appear here either to be completely
in lines where rods are to be formed: 1
^^y^^^^ ^.^ to fuse together. The
enamel cells containing caleo-spherites ; :!, ^ b
globules arranged to form rods; 3, first- loWCr part of the cell COntainS the
forming layer of enamel : 4, dentin. 1 ,, ^ ^ )5 1 • 1
larger " enamel drops, which merge
without sharp boundaries into the substance of the enamel rods. This
then appears as a part of the enamel cell, in which the originally iso-
lated "enamel drops" have run together into a continuous mass, and
the growth of the enamel rod, once begun, appears to take place by the
addition of new " enamel drops."
The minute globular forms described by Dr. Sj^ee are calco-s])herites
;
the larger ones, his " enamel drops," are globules of calco-globulin which
are to form the rods (Fig. 72).
Appearances of calcified fibers ])roj('cting beyond the line of calci-
fication are seen when studying sections of forming young enamel, and
these are evidences that fine processes of fibers from the cells of the
stratum intermedium pass down through and among the ameloblasts to
the forming enamel beneath. These are probably the processes which
i\rr. Tomes saw and descrilied as connecting the enamel cells with the
stratum intermedium. If one separates slightly the enamel cells from
the stratum intermedium the j^arted cells will have the appearance of
broken processes or fibers, and we may be able to see fibers crossing
from the enamel cells to the stratum intermedium.
A longitudinal section of a human tooth at birth, just after the