books as Harvey on the Circulation of Blood, or even Vesalius on Human
{128} Anatomy. As we have seen, it is now quoted from by our best
recent authorities who attempt seriously to trace the history of the
microbic theory of disease, and its conclusions are the result of
logical processes and not the mere chance lighting upon truth of a
mind that had the theories of the time before it. In it Father
Kircher's genius is best exhibited. It has the faults of his too ready
credibility; and his desire to discuss all possible phases of the
question, even those which are now manifestly absurd, has led him into
what prove to be useless digressions. But on the whole it represents
very well the first great example of the application of the principle
of inductive science to modern medicine. All the known facts and
observations are collected and discussed, and then the conclusions are
suggested.

It is very interesting to trace the development of Father Kircher's
ideas with regard to the origin, causation, and communication of
disease, because in many points he so clearly anticipates medical
knowledge that has only come to be definitely accepted in very recent
times. It has often been pointed out that Sir Robert Boyle declared
that the processes of fermentation and those which brought about
infectious disease, were probably of similar nature, and that the
scientist who solved the problem of the cause of fermentation would
throw great light on the origin of these diseases. This prophetic
remark was absolutely verified when Pasteur, a chemist who had solved
the problem of fermentation, also solved {129} the weightier questions
connected with human diseases. Before even Boyle, however, Father
Kircher had expressed his opinion that disease processes were similar
to those of putrefaction. He considered that putrefaction was due to
the presence of certain _corpuscula_, as he called them, and these he
said were also probably active in the causation of infectious disease.

He was not sure whether or not these _corpuscula_ were living, in the
sense that they could multiply of themselves. He considered, however,
that this was very probable. As to their distribution, he is
especially happy in his anticipations of modern medical progress.
While he considered it very possible that they were carried through
the air, he gives it as his deliberate opinion that living things were
the most frequent agents for the distribution of the corpuscles of
d