54 W. H. F. ADDISON AND J. L. APPLETON, JR. 
The pulp-chamber has the characteristic shape found in all 
permanently growing teeth, as is well seen, for instance, in the 
elephant’s incisor. Its cross-area is greatest at the basal end of 
the tooth, and gradually diminishes anteriorly. The pulp- 
chamber is found to extend in the tooth beyond the line of the 
gingivus, and very nearly to the occlusal surface. The shape 
Broke 
/ 
E Ae ye 
A PA 
\ 
anterior end 
JUYIYL 
Fig. 6 Upper incisor of a 5-month albino rat (X< 5) and cross-sections of it 
at different points (X 8), to show the relative cross-area of the dentine and of 
the pulp chamber at these regions. The dotted line indicates the position of 
the margin of the alveolus. 
in cross-section of the pulp-chamber at different levels may be 
seen by reference to figure 6. The position of the filled-in pulp- 
chamber is usually well marked on the occlusal surfaces as a 
line (fig. 5). In weathered specimens of rats’ teeth from recent 
geological formations this last-formed part which fills in the pulp- 
chamber at the end of the tooth, is usually found to be lacking, 
and is evidently not of the same hardness as the surrounding 
parts of the tooth. 
