Page 63 - My FlipBook

indeed, it was difficult to disting^uish species, different species
being so nearly alike, physically and morphologically. It re-
quired the patience and the skill of such as Pasteur to dis-
tinguish and separate species. Very few men would under-
take it; very few men could spend the time that was neces-
sary. And then to keep them pure long enough to study
their characteristics was another matter of extreme difficulty.
Pasteur put them in flasks, to which he had drawn out long
crooked glass necks with bulbs here and there containing
water, so that micro-organisms entering might be caught in
these little bulbs of water, etc., trying to admit the air and yet
keep his growths free from contamination with other species.
In 1854 Schraeder conceived the idea that he could cork a tube
with cotton and that the cotton would form a filter that would
prevent the ingress of any particles floating in the air. This
was successful, and has been used by bacteriologists from
that day to this. The chemists claimed that it was not the
micro-organisms, but decomposing gaseous material in the
atmosphere that had these peculiar molecular motions of
which they spoke that passed in and set up these fermenta-
tions, and also that oxygen was necessary to the fermenta-
tions. But with the cotton stopper they excluded the parti-
cles, the spores, the micro-organisms that were floating in
the air, admitted the oxygen and gaseous accompaniments
freely, and yet, no decomposition would occur.
Now, perhaps I can bring the difficulties of making these
cultivations more strongly to your mind by calling your at-
tention to the habits of plants. If we go into the woods we
will find the oaks, the hickories, the elms, the chestnuts and
other varieties of trees growing in association, and with them
a great variety of underbrush, perhaps. That is the habit
of plants. True, there will be a partial segregation of plants,
a grove composed mostly of oaks, mostly of hickories or
mostly of maples, but not entirely. There is a partial segre-
gation of plants due to varieties of soil. The plants which I
have named grow best upon our alluvial soil, but the pines
grow best upon sandy or rocky soil. If we go into the fields
or the meadows we find the grasses, the weeds, the flowers
growing in association. Now, it is just so with micro-organ-
isms ; wherever we find the conditions for the growth of
micro-organisms we will find varieties of micro-organisms

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