The Black Death

All these phenomena were observed with horrified accuracy by contemporary writers and reported with care and objectivity. Little or no effort was made, however, to explain them logically or to work them into a coherent pattern; the background of knowledge against which such an attempt could have been made was woefully inadequate and the will to try rarely present. One subject which proved something of an exception was the problem of how the disease passed from man to man and country to country. To this much thought was given and many esoteric theories were put forward. Fundamentally there were two, by no means mutually exclusive, schools of thought: those who believed in person-to-person infection and those who pinned their faith in the existence of a ‘miasma’ or poison cloud.

The medieval doctor was confronted with a situation where a large number of people died suddenly and inexplicably in a given area. This zone of mortality shifted constantly but gradually, conquering new territory and abandoning old. Any rational being, faced with such a phenomenon but totally unversed in medical lore, would be likely to arrive at the same explanation. There must be some vicious property in the air itself which travelled slowly from place to place, borne by the wind or impelled by its own mysterious volition. There were many different points of view as to the nature of this airborne menace, its origin, its physical appearance. But almost every fourteenth-century savant or doctor took it for granted that the corruption of the atmosphere was a prime cause of the Black Death.

Debate generally centred on the degree of harm which this corruption might do to the atmosphere which it affected. Ibn Khātimah, the Arab philosopher and physician from Granada, took an extreme line when he argued that corruption might in certain cases be absolute; that is to say that the very nature of the air might be permanently changed by putrefaction.^{25} In such air no light would burn, still less could a man hope to live. Such conditions existed only in the very heart of a plague-ridden area, all around was to be found a zone of partial corruption where the danger of death, though still great, was no longer inescapable. A change in the composition of the air might be caused by the movement of the stars or the putrid fumes of decaying matter; in the case of the Black Death, however, Ibn Khātimah believed that the cause was to be found in the vagaries of the weather over the previous few years.

Not many people agreed with the theory that the air could be altered in its very composition. Even Ibn Khātimah’s colleague and friend, Ibn al Khatīb, could not accept that there was more than a temporary poisoning caused by the addition of something noxious to the atmosphere.^{26} What that something was and where it came from was similarly a topic for hot debate. Alfonso of Cordoba, like most men of learning at the time, considered that movements of the planets probably started the mischief but held that, if the poisoning of the atmosphere went on for any length of time, then some human agency must be behind it:

since air can also be infected artificially, as when a certain confection is prepared in a glass flask, and when it is well fermented, the person who wishes to do that evil waits till there is a strong, slow wind from some region of the world, then goes into the wind and rests his flask against some rocks opposite the city or town which he wishes to infect and, making a wide detour and going further into the wind lest the vapours infect him, pulls his flask violently against the rocks. When it breaks the vapour pours out and is dispersed in the air, and whoever it touches will die…^{27}

The anonymous author of another plague tractate rejected all such fantasies of medieval gas warfare and made the great earthquakes of 1347 the villains of the piece.^{28} Even before this date, pressure had been building up underground and a few noxious currents of air which had escaped had started minor epidemics. But now poisonous fumes poured forth through cracks in the earth, escaped into the atmosphere and drifted around the face of Europe killing all who encountered them.