They had seen the ravages of these epidemics continue for months or even years, notwithstanding the fact that multitudes of God-fearing people prayed hourly that such ravages might be checked.

And they must have observed also that when even very simple rules of cleanliness and hygiene were followed there was a diminution in the ravages of the plague, even without the aid of incantations.

Such observations as these would have a tendency to awaken a suspicion in the minds of many of the physicians that disease was not a manifestation of the supernatural, but a natural phenomenon, to be treated by natural methods.
But, be the causes what they may, it is a fact that the thirteenth century marks a turning-point, or the beginning of an attitude of mind which resulted in bringing medicine to a much more rational position.
Among the thirteenth-century physicians, two men are deserving of special mention.

These are Arnald of Villanova (1235-1312) and Peter of Abano (1250-1315).

Both these men suffered persecution for expressing their belief in natural, as against the supernatural, causes of disease, and at one time Arnald was obliged to flee from Barcelona for declaring that the "bulls" of popes were human works, and that "acts of charity were dearer to God than hecatombs." He was also accused of alchemy.
Fleeing from persecution, he finally perished by shipwreck.
Arnald was the first great representative of the school of Montpellier.
He devoted much time to the study of chemicals, and was active in attempting to re-establish the teachings of Hippocrates and Galen.
He was one of the first of a long line of alchemists who, for several succeeding centuries, expended so much time and energy in attempting to find the "elixir of life." The Arab discovery of alcohol first deluded him into the belief that the "elixir" had at last been found; but later he discarded it and made extensive experiments with brandy, employing it in the treatment of certain diseases--the first record of the administration of this liquor as a medicine.