Page 64 - My FlipBook

growing. True, there is some segregation there, some va-
rieties that grow best in rotting wood ; another class of
varieties grow best in fruits or in vegetables ; another class
of varieties grow best in decaying flesh, and so on, yet in
each of these localities we will find many varieties growing
together.
It was the separation of these varieties that was gi.ving
the difficulty. This went on until a discovery was made by
Dr. Koch, then an obscure physician living in a small town in
Germany. His proposition was to plant the spores of micro-
organisms, taking them wherever we find them mixed to-
gether as they were, by putting them in a gelatin made liquid
by heat and shaking them up until they were divided and
separated, putting very little of the matter containing the
micro-organisms in a large amount of gelatin, then pouring
that onto plates he would allow it to cool and each spore
would develop a colony to itself ; they were not able to move
about, and when a colony had developed he would pick up a
little material from that colony, plant it into another medium
and have a colony all the members of which had developed
from a single spore, and in this way obtaining pure varieties
for purposes of study. Not only did he invent this particular
plan of cultivating micro-organisms by which we could
separate species distinctly, but he discovered means of stain-
ing them so that they came clearly into view in the field of
the microscope. From that time on (and that is only about
twenty years ago) the study of micro-organisms has gone on
with wonderful rapidity; indeed, before that it was almost
impossible to study micro-organisms with any degree of ac-
curacy.
But this media upon which they were planted had to be
purified. It would be difficult for you to go into the fields
and find a patch of earth that had in it no seeds of plants.
It was found impossible to select a material in which micro-
organisms would grow that had no spores of micro-organ-
isms. These had to be removed before such media was suited
to the planting and cultivation of micro-organisms, and a
vast amount of experimenting was done along that line. The
earlier method was to destroy these by boiling, but that was
found to be ineffective, for while the living plants—the grow-
ing plants—might be killed, in many instances the spores