48 SPECIAL HISTOLOGY. 



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

 dentine of Owen. 1 



1 [Considerable discrepancies will be met with if we compare the various state- 

 ments of authors who have described the ultimate structure of tbe dentine. 



1. According to Retzius, the dentine contains cell$,hxxt 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 onejmother, 

 as the "osteal cells" of Tomes and De Morgan (to which we have referred in the 

 note to § 107, p. 377, vol. I), have to osseous lacunae. 



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

 M 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 under- 

 stand 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 cellu- 

 lar." In perfect accordance with this, we find, on referring to plate 123, fig. 1, 

 which represents a section of human dentine, that the "dentinal cells" which are 

 marked did! , are traversed by from seven to eleven dentinal tubules. 



But at p. 463, the passage in which reference is made to this figure, runs thus : 

 "the dentinal cells of the human tooth are subcircular, about g^th of an inch in 

 diameter. They seem most numerous from being most conspicuous near the peri- 

 phery 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 cal- 

 cified primary 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 g^th of an inch in diameter, can have passing 

 through it seven tubules, each of which is Ts,W^ n °^ an * ncn m diameter ? To 

 say nothing of the circumstance, that these tubules are at the very least toJooo** 1 

 of an inch apart. Halve the actual diameter of the tubules and arrange them 

 close together, and they will barely squeeze into g^th of an inch. We conclude, 

 therefore, as the definitions and the figures of these dentinal cells are at variance, that 

 we are not justified in making any definite 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 

 previouslyvery 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 

 Appearances occurring in the Dentine, dependent on its mode of Calcification, 

 • Quarterly Journ. of Mic. Science,' vol. I, p. 252, 1853,) has confirmed Czermak's re- 

 sults, 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 



