The Bible tells of a number of epidemics and in each case it is the anger of God kindled against sinners, as in 2 Samuel 24. In New Testament times, the theory of demonic possession as an explanation of disease was popular, and both Jesus and others cast our devils. The biblical authority for this has caused the theory to persist to this day, as witness by the popularity of such movies as The Exorcist. As long as disease was blamed on divine or demonic influ- ences, something as mundane as contagion was overlooked. Fortu- nately, the Bible also contains instructions for isolating those with leprosy (a name given not only to leprosy itself, but to other, less serious skin conditions). The biblical practice of isolation was for religious rather than hygienic reasons, for leprosy has a very low infectivity. On biblical authority, lepers were isolated in the Middle Ages, while those with really infectious disease were not. The prac- tice of isolation, however, caused some physicians to think of it in connection with disease generally. In particular, the ultimate terror of the Black Death helped spread the notion of quarantine, a name which referred originally to isolation for forty (quarante in French) days. The fact that isolation did slow the spread of a disease made it look as though contagion was a factor. The first to deal with this possibility in detail was an Italian physician, Girolamo Fracastoro (1478–1553). In 1546, he suggested that disease could be spread by direct contact of a well person with an ill one or by indirect contact of a well person with infected articles or even through transmission over a distance. He suggested that minute bodies, too small to be seen, passed from an ill person to a well one and that the minute bodies had the power of self-multiplication. It was a remarkable bit of insight, but Fracastoro had no firm evidence to support his theory. If one is going to accept minute unseen bodies leaping from one body to another and do it on noth- ing more than faith, one might as well accept unseen demons. Minute bodies did not, however, remain unseen. Already in Fracastoro’s time, the use of lenses to aid vision was well es- tablished. By 1608, combinations of lenses were used to magnify distant objects and the telescope came into existence. It didn’t take much of a modification to have lenses magnify tiny objects. The Italian physiologist Marcello Malpighi (1628–94) was the first to use a microscope for important work, reporting his observations in the 1650s.
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