From Aristotle to Galen, that is, for the space of five centuries, the anatomy of the dental system, so far as may be deduced from the writings preserved to us, made no sensible progress. But in respect to this, one must take into consideration some historical facts of capital importance. The school of medicine of Alexandria, which arose about three centuries before Christ, numbered among its most brilliant luminaries the celebrated doctors Herophilus and Erasistratus, who were the initiators of the dissection of human corpses,[100] thus giving a great impulse to anatomical research. It is, therefore, hardly admissible that these two great anatomists, who studied with profound attention even the most complicated internal organs, should have neglected the anatomy of the teeth. Unfortunately, however, not all the results of their researches have come down to us; nor is this to be wondered at, especially if we reflect on the large number of precious works entirely lost by the destruction of the celebrated library of Alexandria, A.D. 642. When we come to speak of Archigenes, we shall see how he, in certain cases, advised trepanning the teeth. This would lead to the belief that in his times, viz., toward the end of the first century after Christ, the existence of the central cavity of the tooth was not ignored, and that, therefore, the structure of these organs had already been the object of study. As to diseases of the teeth and their treatment, there is no doubt that Herophilus and Erasistratus must have occupied themselves with these subjects; and the same may be asserted of Heraclides of Tarentum, a celebrated doctor who lived in the third century before the Christian era. Indeed, we read in Cœlius Aurelianus,[101] that the record had come down through the works of Herophilus and Heraclides of Tarentum, of persons having died by the extraction of a tooth.[102] The same writer also alludes to a passage of Erasistratus, relating to the _odontagogon_ already mentioned, which was exhibited in the temple of Apollo, and to the practical signification to be attributed to the fact of this instrument being of lead and not of hard metal. Now, if Herophilus, Heraclides of Tarentum, and Erasistratus all spoke of the serious peril to which the extraction of a tooth may give rise, and therefore recommended not having recourse to it too lightly, it is evident that they had given serious attention to this operation and consequently also to the morbid conditions that may render it necessary. CHAPTER VI. DENTAL ART AMONG THE ETRUSCANS.