er famous
prescription to bring about the spontaneous generation of mice. What
was needed was a jar of meal kept in a dark corner covered by some
soiled linen. After three weeks these elements {133} would be found to
have bred mice. Too much must not be expected, then, of Kircher in the
matter of crediting supposedly scientific traditions.

It may seem surprising that Father Kircher's book did not produce a
greater impression upon the medical research work and teaching of the
day and lead to an earlier development of microbiology. Unfortunately,
however, the instruments of precision necessary for such a study were
not then at hand, and the gradual loss of prestige of the book is
therefore readily to be understood. The explanation of this delay in
the development of science is very well put by Crookshank, who is the
professor of comparative pathology and bacteriology at King's College,
London, and one of the acknowledged authorities on these subjects in
the medical world. Professor Crookshank says, at the beginning of the
first chapter of his text-book on bacteriology, in which he traces the
origin of the science, that the first attempt to demonstrate the
existence of the _contagium vivum_ dates back almost to the discovery
of the microscope:--[Footnote 11]

[Footnote 11: _A Text-Book of Bacteriology_. Including the
Etiology and Prevention of Infectious Diseases By Edgar M.
Crookshank. Fourth Edition London, 1896]

Athanasius Kircher nearly two and a half centuries ago expressed his
belief that there were definite micro-organisms to which diseases
were attributable. The microscope had revealed that all decomposing
{134} substances swarmed with countless micro-organisms which were
invisible to the naked eye, and Kircher sought for similar organisms
in disease, which he considered might be due to their agency. The
microscopes which he describes obviously could not admit of the
possibility of studying or even detecting the micro-organisms which
are now known to be associated with certain diseases; and it is not
surprising that his teaching did not at the time gain much
attention. They were destined, however, to receive a great impetus
from the discoveries which emanated not long after from the father
of microscopy, Leeuwenhoek.

This reference to Kircher's work, however, shows that more cordial
appreciation of his scientific genius has come in our day, and it
seems not unlikely tha