THE TEETH. 475 



rounded cavities, like osseous lacunae, constituting the so-called osteo- 

 dentine of Owen.* 



* [Considerable discrepancies will be met with if we compare the various statements of 

 authors who have described the ultimate structure of the dentine. 



1. According to Retzius, the dentine contains cells, but these cells, in his view, are cavities 

 analogous to bone lacuna, in which the dentinal canals terminate. 



2. Mr. Nasmyth took a totally different view from this. The matrix, or, as he calls it, 

 " interfibrous substance of the dentine," is, he says, composed entirely of cells; but these 

 cells are solid bodies, lie between, and form the boundaries of the canals. His "cells" and 

 those of Retzius had exactly as much, or as little relation to one another, as the "osteal cells" 

 of Tomes and De Morgan (to which we have referred in the note to 107, p. 335), have 

 to osseous lacunae. 



3. Professor Owen likewise affirms that the dentine is made up of" cells" his " dentinal 

 cells," which, however, can hardly be identical with Czermak's "dentine globules,' as 

 stated in the text. We find it, in fact, somewhat difficult to understand what these " dentinal 

 cells" are, inasmuch as we are unable to reconcile the various definitions of their nature 

 which may be found in the " Odontography." In the first place, at p. 462, it is stated, in a 

 note, that "the true dentinal or calcigerous cells include many tubes and intertubular spaces, 

 and it is much more exact to say, that those cells contain a tubular structure, than that the 

 interstitial space is cellular." In perfect accordance with this, we find, on referring to plate 

 J23, fig. 1, which represents a section of human dentine, that the "dentinal cells" which 

 are marked d'd', are traversed by from seven to eleven dentinal tubules. 



But at p. 403, the passage in which reference is made to this figure, runs thus: " the den- 

 tinal cells of the human tooth are subcircular, about ^^th of an inch in diameter. They 

 seem most numerous from being most conspicuous near the periphery of the dentine, as 

 originally described by me in the dentine of the Crocodile." 



And in the Introduction, p. xlvi. we find : "The diameter of the dentinal or calcified pri- 

 mary cells of the pulp, is usually one-fourth or one-half larger than that of the blood-discs 

 manifest in them." 



Now, how is it possible, that a body s^th of an inch in diameter, can have passing 

 through it seven tubules, each of which is jjj^jj^th of an inch in diameter? To say nothing 

 of the circumstance, that these tubules are at the very least y^^th of an inch apart. 

 Halve the actual diameters of the tubules and arrange them close together, and they will 

 barely squeeze into j^^th of an inch. We conclude, therefore, as the definitions and the 

 figures of these dentinal ceils are at variance, that we are not justified in making any defi- 

 nite statement about them. 



4. Mr. Tomes asserts in his lectures, that the " intertubular tissue is itself made up of 

 minute granules closely united," which pass into those of his "granular layer ;'' an opinion 

 which seems to us to be most nearly in accordance with fact. We may observe, that the 

 dentine globules and interglobular spaces of Czermak, had been previously very carefully 

 figured and described by Mr. Tomes, in his lectures, p. 45. 



5. The views of Czermak are stated in the text. Mr. James A. Salter (On certain Ap- 

 pearances occurring in the Dentine, dependent on its mode of Calcification, " Quarterly 

 Journ. of Mic. Science," vol. I., p. 252, 1853), has confirmed Czermak's results, and has 

 added some very interesting observations of his own. He considers that the contour lines, 

 which he prefers to call " contour-markings," may arise from various causes, not only from 

 those pointed out by Czermak curvings and local enlargements of the canals and inter- 

 lobular spaces, but also from a difference in density without alteration of structure ; and he 

 states as a general law, that the curves of the contour markings are in proportion to the 

 primary curves of the dentinal tubes at any particular spot, and cross them at right angles. 

 No markings are more divergent than the outline of the tooth, and passing from within out- 

 ward, they abut in succession upon the external surface of the dentine, under the enamel 

 and crusta petrosa, in the form of granular patches. The outer extremities of these patches 



