RAINEY, ON DENTAL TISSUES. Pay 
teeth in the shortest space of time, and with the feeblest acid, 
is to suspend them by a thread in a moderately large quantity 
of the acidified fluid. One part, by measure, of hydrochloric 
acid, with twelve of water, will serve very well for this 
purpose; but the solution may be weaker if preferred. 
Globular dentine of the human tooth, as observed by Mr. 
Salter, may be easily obtained by introducing the point of a 
penknife into the hollow of a half-grown fang and scraping 
its inner surface ; or, which is better, by chipping off the free 
edge of the opening into the fang. 
The previous decalcification will not be applicable to 
enaniel, which, containing so little soft material, 1s lacerated 
and torn into pieces by the effervescence occasioned by the 
action of the hydrochloric acid upon the carbonate of lime it 
contains. However, this tissue is well seen in young cusps, as 
will be shown hereafter. For the examination of the true 
nature of the so-called dentinal tubules, the sections of the 
decalcified dentine must be of different kinds; some being 
parallel with the pulp-cavity, and others at right angles to it. 
In such sections, when compared with similar ones of teeth 
not decalcified, it will be seen that the form and bulk of the 
decalcified dentine-rods and -globules are not altered, and that 
they are only distinguishable from those of the perfect 
dentine by an inferior degree of brightness. This gives an 
advantage to the decalcified specimens when employed for 
microscopic purposes. The exact form, extent, and precise 
situation of the dentinal interspaces are best defined in these, 
in consequence of the lower refractive power of the material 
by which they are surrounded interfering less with accurate 
definition. By such a mode of procedure it will be seen that 
dentine is made up of solid rods or fibres of a quadrilateral 
figure (fig. 6) running in different directions from the pulp- 
cavity towards the external surface, some being parallel with, 
others at right angles to that cavity, and a third set passing 
in all the directions intermediate between these extremes. At 
each of the four angles of all these rods a space, or so-called 
tubule, exists (fig. 6 6), being formed by the meeting of the 
four adjacent angles of the four contiguous rods (fig. 6 a). 
This interval is more or less limited to the pomt of conflux 
of these rods in different parts of a tooth, the difference 
depending upon the degree of coalescence of contiguous rods. 
Sometimes it extends some distance between each two adja- 
cent rods, whence the appearance of a dichotomous division 
of a space is produced. On the contrary, in other parts the 
coalescence of the adjoining fibres or rods is so complete, 
that not only the spaces between the apposed surfaces of the 
