t may exist in the air. The air itself will re-enter very gradually,
and slowly enough to enable any dust to be taken up by the drop of water
which the air forces up the curvature of the tube. Ultimately the tube
will be dry, but the re-entering of the air will be so slow that the
particles of dust will fall upon the sides of the tube. The experiments
show that with this kind of vessel, allowing free communication with the
air, and the dust not being allowed to enter, the dust will not enter
at all events for a period of ten or twelve years, which has been the
longest period devoted to these trials; and the liquid, if it were
naturally limpid, will not be in the least polluted neither on its
surface nor in its mass, although the outside of the flask may become
thickly coated with dust. This is a most irrefutable proof of the
impossibility of dust getting inside the flask.

"The wort thus prepared remains uncontaminated indefinitely, in spite
of its susceptibility to change when exposed to the air under conditions
which allow it to gather the dusty particles which float in the
atmosphere. It is the same in the case of urine, beef-tea, and
grape-must, and generally with all those putrefactable and fermentable
liquids which have the property when heated to boiling-point of
destroying the vitality of dust germs."(7)

There was nothing in these studies bearing directly upon the question
of animal diseases, yet before they were finished they had stimulated
progress in more than one field of pathology. At the very outset
they sufficed to start afresh the inquiry as to the role played by
micro-organisms in disease. In particular they led the French physician
Devaine to return to some interrupted studies which he had made ten
years before in reference to the animal disease called anthrax, or
splenic fever, a disease that cost the farmers of Europe millions of
francs annually through loss of sheep and cattle. In 1850 Devaine had
seen multitudes of bacteria in the blood of animals who had died of
anthrax, but he did not at that time think of them as having a causal
relation to the disease. Now, however, in 1863, stimulated by Pasteur's
new revelations regarding the power of bacteria, he returned to the
subject, and soon became convinced, through experiments by means of
inoculation, that the microscopic organisms he had discovered were the
veritable and the sole cause of the infectious disease anthrax.

The publication of this