THE TEETH OP MARSUPIAL ANIMALS. 
411 
Others pass into each other, and are so gradually and intimately blended that it 
would be impossible to determine to which tissue a given point belonged. 
The facts that I have stated lead, I think, to two conclusions. First, that the existence 
of fully developed tubes in the enamel continuous with those of the subjacent dentine, 
is common to the teeth of at least the great majority of marsupial animals, if not all, 
excepting the Wombat. And, secondly, that the enamel and dentine are so closely 
related, that the one should almost be regarded as a modification of the other, rather 
than as a tissue of a wholly different nature. 
The sections from which the foregoing descriptions have been written, form part of 
an extensive series in my possession. The accuracy of the statements may therefore 
at any time be tested. 
I remain, my dear Sir, yours faithfully, 
June 20th, 1849. John Tomes. 
To Robert E. Grant, M.D., F.R.S. 
Explanation of the Plates. 
PLATE XXXV. 
Fig. 1. A section from crown of a molar tooth of Macropus giganteus, showing the 
tubes of the dentine A in the latter part of their course, and continued into 
the enamel B, that part only near the dentine being shown. C, a continu- 
ous dentinal and enamel tube more highly magnified. 
Fig. 2. A transverse section through the lower incisor of the same animal. A, the 
dentine. B, the enamel in its whole thickness, showing the curves of the 
fibres. 
Fig. 3. The apex of one of the tubercles from the crown of a molar tooth of Macropus 
giganteus, showing the whole thickness of the enamel, B, containing cells 
in the contour lines, and showing also the spiral course of the enamel 
tubes near the apex of the tubercles. A, the dentine. 
Fig. 4. A longitudinal section from a premolar tooth of Hypsiprymnus penicillatus, 
showing the outer part of the dentine A, and the whole thickness of the 
enamel B, with the tubes in each. C, the same more highly magnified. 
Fig. 5. A longitudinal section from a lower incisor of the Wombat, showing the 
dentine A, with the manner of termination of the dentinal tubes. B, the 
enamel, and C, the cement. 
Fig. 6. A longitudinal section of a tubercle from a molar of Phalangista vulpina, 
showing A, the dentine, and B, the enamel with their tnbes. 
