Excerpt from Journal of the British Dental Association, Vol. 23: A Monthly Review of Dental Surgery; January to December, 1902

I have said that I wish-to avoid controversial matters as far as I can in my remarks to-day; but I cannot wholly avoid touching upon them if I am to give you, a summary of the more important work in progress. I have referred to the early stages of dental caries as a process of destruction of the cement substance between the enamel rods. Not long after the appearance of my first paper on this subject Dr. Otto Walkhoff published a contribution to the histology of enamel in which he claimed that there is no cement substance in this tissue and that the enamel rods are in actual contact. Obviously, if this claim were true the views which I had published concerning the early stages of decay would have to be somewhat modified. I therefore undertook to re-investigate this subject of enamel structure. Dr. Walkhoff begins his criticisms by saying that misinterpretation of enamel structure is almost certain to follow a study of longitudinal sections. As applied to the beginner this criticism is no doubt well founded. In any event, I agree with him that transverse sections are much to be preferred for purposes of critical study. Dr. Walkhoff then proceeds in an attempt to Show that the appearance of cement substance between the enamel rods is due to inaccurate focusing or to the use of objectives having too low a numerical aperture. I may say in passing, that my own work was done-with the very lens so highly recommended by Dr. Walkhoff, the Zeiss apochromat., 3 mm. Focus, numerical aperture and I can endorse all that he says about the superb optical qualities of this objective. For purposes of illustration Dr. Walkhoff introduces photographs of the diatom Triceratium favus, showing that, as the surface of this diatom is convex, the outer edges must be out of focus when the centre is in focus, and he claims that these outer, out-of-focus portions of the picture Show how an appear ance of cement substance may be obtained in a transverse section of enamel (fig. Well, I Show you a photograph of this diatom, the centre of which is in critical focus, and you will see, just outside of the area of perfect focus, diffraction lines as described by Dr. Walkhoff, and nearer the outer edge, where the focus is still more imperfect, an appearance of rods embedded in cement substance.

About the Publisher

Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com

This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.