This plague, thought to be the Bubonic plague, spread throughout Europe, killing about half its population. It was called the Black Death because of the black blotches that appeared on the victims' bodies. This plague was carried by infected fleas of the black rat.
Theology, developed in accordance with this idea, threw about all cures, even those which resulted from scientific effort, an atmosphere of supernaturalism. The vividness with which the accounts of miracles in the sacred books were realized in the early Church continued the idea of miraculous intervention throughout the Middle Ages. The testimony of the great fathers of the Church to the continuance of miracles is overwhelming; but everything shows that they so fully expected miracles on the slightest occasion as to require nothing which in these days would be regarded as adequate evidence.
In this atmosphere of theological thought medical science was at once checked.
The School of Alexandria, under the influence first of Jews and later of Christians, both permeated with Oriental ideas, and taking into their theory of medicine demons and miracles, soon enveloped everything in mysticism. In the Byzantine Empire of the East the same cause produced the same effect; the evolution of ascertained truth in medicine, begun by Hippocrates and continued by Herophilus, seemed lost forever. Medical science, trying to advance, was like a ship becalmed in the Sargasso Sea: both the atmosphere about it and the medium through which it must move resisted all progress. Instead of reliance upon observation, experience, experiment, and thought, attention was turned toward supernatural agencies.
Oriental Rat Flea:
Fleas are blood sucking parasites. They have the potential of spreading dangerous diseases to humans and other animals. It is possible the first flea was native to Africa and traveled by boat on the back of...