he teeth must be
rubbed with suitable dentrifices before going to bed, or else
in the morning before breakfast. Although Avicenna recommended
various oils for this purpose, Giovanni of Arcoli appears
very hostile to oleaginous frictions, because he considers
them very injurious to the stomach. He observes, besides, that
whilst moderate frictions of brief duration are helpful to the
teeth, strengthen the gums, prevent the formation of tartar,
and sweeten the breath, too rough or too prolonged rubbing is,
on the contrary, harmful to the teeth, and makes them liable
to many diseases."

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 adde