reconcile physicians and philosophers. But his researches were
not confined to medicine, for he seems to have had an inkling of
the hitherto unknown fact that air possesses weight, and his
calculation of the length of the year at three hundred and
sixty-five days, six hours, and four minutes, is exceptionally
accurate for the age in which he lived. He was probably the first
of the Western writers to teach that the brain is the source of
the nerves, and the heart the source of the vessels. From this it
is seen that he was groping in the direction of an explanation of
the circulation of the blood, as demonstrated by Harvey three
centuries later.

The work of Arnald and Peter of Abano in "reviving" medicine was
continued actively by Mondino (1276-1326) of Bologna, the
"restorer of anatomy," and by Guy of Chauliac: (born about 1300),
the "restorer of surgery." All through the early Middle Ages
dissections of human bodies had been forbidden, and even
dissection of the lower animals gradually fell into disrepute
because physicians detected in such practices were sometimes
accused of sorcery. Before the close of the thirteenth century,
however, a reaction had begun, physicians were protected, and
dissections were occasionally sanctioned by the ruling monarch.
Thus Emperor Frederick H. (1194-1250 A.D.)--whose services to
science we have already had occasion to mention--ordered that at
least one human body should be dissected by physicians in his
kingdom every five years. By the time of Mondino dissections were
becoming more frequent, and he himself is known to have dissected
and demonstrated several bodies. His writings on anatomy have
been called merely plagiarisms of Galen, but in all probability
be made many discoveries independently, and on the whole, his