218 RAINEY, ON DENTAL TISSUES. 
rods, but also the intervals at the junction of their angles, are 
obliterated. In such cases dentinal tubules are said not to be 
present. Now when a thin section is made through such an 
assemblage of fibres and passages as above described, and as 
represented in Pl. XII, fig. 6, the cut rods will present 
sections of various forms, some will be nearly square, others 
diamond shaped, and a third set linear ; these forms depending 
upon their several directions —and from what has been 
before stated concerning the directions of these fibres, it 
is obvious that the forms will gradually pass one into the 
other. / 
The subjoined diagram (fig. 2) representing a vertical sec- 
tion of a tooth at a more advanced stage than the former 

Fig. 2. 
e, enamel; d, dentine; o-d, osteo-dentine; g-d, globular dentine ; m, ma- 
trix. The horizontal line represents the part from which the section, a 
portion of which is figured in Pl. XI, fig. 6, was taken. 
one, will illustrate the various points spoken of, as well as 
the reason for the different forms on section of dentine-rods. 
Now if these rods had inclosed tubes of the form repre- 
sented in plates intended to show them, their sections must 
have presented first circular areas, and then ovals, becoming 
gradually more and more excentric until they ended in straight 
lines. But such is not the case; the sections of these spaces, 
at first more or less circular, become angular or arrow-shaped, 
the before-mentioned lines diverging from the angular point 
losing themselves between the contiguous rods, the depths to 
which these lines extend depending upon the amount of their 
