i Sage a ye 
i, 2 
194 THe MIcROSCOPE. 
arranged parallel, some standing vertical to the dentine and others 
nearly parallel with it; this crossing of the bundles producing the 
markings. 
The enamel prisms are about 7455 of an inch in diameter and 
are separated by a fine interstitial cement substance. The outline 
of the prisms, or rods, is not straight, but wavy. Hydrochloric 
acid causes them to break up into small cubie fragments of about 
equal siz, these pieces correspond to the cross 
striations seen on the surface of rods isolated by 
means of some acid. Figure 2, A, shows the 
isolated fibres with their wavy outlines and cross 
striations; while B, of the same figure, shows the 
appearance of the rods in transverse section. In 
young teeth, this enamel is covered with a deli- 
cate membrane, Nasmyth’s membrane, but in adult 
teeth it has disappeared, having been worn away. 
In the deeper parts of the enamel, near the 
dentine, there are longer or shorter canals -be- Fig. 2, 
‘tween the bundles of prisms. These 
lead into the interglobular spaces of 
Czermak, described below. 
The dentine (Fig. 1, No. 2,) com- 
FZ: = poses the great bulk of the hard part 
pee, iscave Ti als of the tooth. It has a firm matrix 
Soe ale 
HN 
vil HN 
Wil 
: 
a” 
pierced with a number of minute can- 
als, known as the dentinal tubes. These 
tubes are branched, commence at the 
pulp cavity, extend spirally outwards, 
become finer and finer, and finally ter- 
minate at the surface of the dentine, in 
larger or smaller cavities, known as the 
| 
interglobular spaces of Czermak. These 
spaces contain branched, nucleated 
cells, not unlike those found in the 
lacunze and canaliculi of bone. The 
dental tubes are lined with a sheath, 
| dentinal sheath, and in these sheaths are 
g. 3. ue the dentinal fibres of Tomes. The denti- 
nal fibres appear to anastomose with the processes of the cells 
F 
