THE DENTAL TISSUES OF THE ORDER RODExNTIA. 
561 
and branch much more freely than in the incisors: I do not know a more beautiful 
microscopic object than a fine longitudinal section of the molar tooth of a common 
Hare. The enamel, where it exists as a thin layer lining the inflected parts of the 
confluent denticles, is composed of short fibres, which leave the dentine at a wide 
angle, and towards their terminal extremities turn a little downwards. But when this 
tissue invests the outer and more exposed parts of the tooth the amount is much 
greater ; in these parts the enamel is divisible into two portions, the inner of which 
is composed of straight, uniform and parallel fibres, and the outer part of continua- 
tions of the same fibres, but bent about somewhat irregularly, and approaching in 
places to a confluent lamelliform arrangement. The appearances presented in a 
transverse section of a molar tooth are delineated in fig. 52 ; but even in this the 
arrangement of the enamel fibres in the outer portion of the tissue is regular as com- 
pared with what is seen in many parts of the tooth. In the outer part the fibres 
have the appearance of being smaller than those which lie next the dentine, as shown 
in the figure. 
Lepus cuniculus (Linn.). — The dental tissues in the teeth of the Rabbit so closely 
resemble those of the Hare, that I doubt the possibility of telling the one from the 
other, excepting by the external form and size of the entire tooth. The vascular 
canals are perhaps less numerous in the Rabbit. 
Of the following animals I have been able to obtain the molar teeth only. 
Lepus Americanus, Erxl. (Zoological Society). — The vascular canals are very 
numerous and extend to within a short distance of the enamel, where they usually 
terminate in dilated extremities. In their passage they branch rectangularly and 
anastomose with neighbouring canals, a circumstance I have not before observed in 
the vessels of vascular dentine. Each canal becomes surrounded by a layer of trans- 
parent tissue, in which are a few lacunse very similar to those seen in the cement; 
eventually the canals are lost by the encroaching inwards of the transparent tissue, 
and lines of branching cells alone remain to mark their former position. 
The enamel could not be readily distinguished from that seen in the molars of 
Lepus timidus ; a tendency to confluent lamelliform arrangement of the fibres is found 
in places, and as it appears in a longitudinal section is shown in fig. 53. 
In the molar teeth of Lepus aquaticus (Bachm.) and Lepus sylvatlcus (Bachm.), I 
find no characteristic differences in the dental tissue by which they could be distin- 
guished from each other, or from the teeth of either of the preceding species of 
Hares. 
Before leaving the subject of Hares’ teeth, I should state that occasionally fine 
supplemental enamel fibres may be seen crossing the course of the ordinary ones at 
a right angle. They do not exceed the 15,000th of an inch in diasneter, and are not 
constantly present ; indeed I have onl}’ seen them near the basal half of the tooth, 
where the enamel is not perfectly hardened. 
The facts which are recorded in the foregoing pages have been gathered from 
MDCCCL. 4 c 
