All this is so modern in many ways that we might expect a detailed exact knowledge of the anatomy of the teeth and even something of their embryology from Arculanus. It must not be forgotten, however, that coming as he does before the Renaissance, the medical sciences in the true sense of the word are as yet unborn. Men are accumulating information for practical purposes but not for the classification and co-ordination that was to make possible the scientific development of their knowledge. Giovanni of Arcoli's acquaintance with the anatomy of the teeth was rather sadly lacking. He does not know even with certainty the number of roots that the teeth have. This has been attributed to the fact that he obtained most of his information from books, and had not the time to verify descriptions that he had found. It has been argued from this that he was himself probably not a practical dentist, and turned to that specialty only as a portion of his work as a general surgeon, and that consequently he was not sufficiently interested to verify his statements. His chapters on dentistry would seem to bear out this conclusion to some extent, though the very fact that one who was himself not specially interested in dental surgery should have succeeded in gathering together so much that anticipates modern ideas in dentistry, is of itself a proof of how much knowledge of the subject there was available for a serious student of that time. The anatomy of the teeth continued to be rather vague until about the middle of the next century when Eustachius, whose investigations of the anatomy of the head have deservedly brought him fame and the attachment of his name to the Eustachian canal, wrote his "Libellus de Dentibus--Manual of the Teeth," which is quite full, accurate, and detailed. Very little has been added to the microscopic anatomy of the teeth since Eustachius' time. He had the advantage, of course, of being intimately in contact with the great group of Renaissance anatomists,--Vesalius, Columbus, Varolius, Fallopius, and the others, the great fathers of anatomy. Besides, his position as Papal Physician and Professor of Anatomy at the Papal Medical School at Rome gave him opportunities for original investigation, such as were not easily obtained elsewhere.