a and was frequently sent as ambassador to
diverse European princes by the Duke of Ferrara. He was also sent as
ambassador for the Popes into France and Hungary. He died at the
Monastery of Monte Oliveto in the arms of his brother, who was the
Prior of the monastery, but his body was brought for burial to the
Church of St. George in Ferrara. Roverella finds a significant place
in all the histories of the time.

Calixtus III (1455-58).--The physician of Pope Calixtus III and Pius
II was Joannes Serninus. He was a native of Siena, practised for a
time in his native city, was offered the position with a good salary
of public physician to Citta di Castella, then went to Ancona in a
similar position with such success, according to tradition, that his
cures were considered almost miracles. From here he was summoned by
Pope Calixtus III, and after his death {438} was retained as his
physician by Pope Pius II, himself one of the Piccolomini family of
Siena. After his death his body was transferred to Siena because the
city considered that the remains of so great a son should rest in her
soil. It is significant that this physician of wide experience in
public health matters, whose successful career in helping various
Italian towns to make conditions more healthy for their citizens gave
him a wide reputation, should be the chosen physician of Pope Calixtus
III, to whom is attributed a famous Bull, that has never been found
however, against Halley's comet on its appearance in 1456. The
selection of such a man as Serninus as Papal Physician makes it
extremely improbable that the Pope should have issued any such
document as is attributed to him. Its issue has been accepted only
with the thought that in the middle of the fifteenth century the Pope
and his court were buried in ignorance of science and above all of
medicine and the cause of disease. [Footnote 51]

[Footnote 51: The whole subject of the supposed Papal Bull against the
comet is discussed in my sketch of Regiomontanus the father of modern
astronomy, as he is sometimes called, in "Catholic Churchmen in
Science," second series, Phila., Dolphin Press, 1909.]

Another of the physicians of Pope Nicholas V and Calixtus III was
Simon Tebaldi, who came of a distinguished family, one of whom was a
Cardinal. He is called by the historians of the time an illustrious
philosopher and physician of the period.

Paul II (1464-71).--Christopher of Verona is mentioned by Platin