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THE DECAY OF THE TEETH. 125
do not penetrate tlie cavities in the basis-snb.stance of the tissues
of the tooth, but appear only as secon
Abbott's communication, from which these statements are
taken, is accompanied l)y a number of illustrations, of which
one is reproduced in Fig. 54, together with the explanation
aiH'()ni]»anying it.
Fig. 54.
Cross-sectiox of Carious Dentine. After Abbott.
" At a certain distance ti'om the decay the canalieuli look
unchanged, and each contains the central transverse section of
the dentinal liber, with its delicate radiated offshoots (Fig. 54, (/).
Xearer to the decay we meet with moderately enlarged canalieuli,
the center of which is occupied by a cluster of protoplasm, the
granules and threads of which have readily taken up the car-
mine (Fig. 54, h). One step farther we find the canalieuli con-
siderably enlarged, to double or trelde their original size, and
thev are tilled with yellow protoplasm, plainly exhibiting the
net-like ari-angcnu'iit of the li\'ing matter (Fig. 54, c, '), The
