Page 71 - My FlipBook

SIXTH LECTURE. ;
I want to speak this morning of the forms of micro-
organisms, and I will show you some illustrations so as to
render you as familiar with these forms as it is possible in
this way.
The forms of individual micro-organisms are of consider-
able importance, and yet not of as much importance, per-
haps, as some persons would attach to it, or as you would be
likely to attach to it from your knowledge of the forms of the
higher plants. You know the oaks and the varieties of oak
trees by looking at them ; anyone who has become skilled
in forestry will know the pines, or of the varieties of pines,
by the form of the leaves, and by the form of the branches.
You will often be able to tell to what species a tree belongs
by looking at it from a distance. Now, this is not so largely
true of micro-organisms. There are certain forms of micro-
organisms, however, that are important for you to know,
and to be able to use the terms indicating them intelligently
and yet, in the determination of species, we never depend ex-
clusively upon the forms presented by micro-organisms, for
there may be a dozen species that are so nearly of the same
form that we cannot tell them apart by microscopic exami-
nation. We have other means of recognizing species aside
from the forms presented. 'The growth of forms has some-
thing to do with determining the species, and particularly
the appearance of the plant upon agar-agar, upon gelatin and
other culture media. We depend more upon the appearance
in growth, in bulk or upon the effects produced upon the
media in the determination of species than we do upon the
forms presented by the individual micro-organisms. But it is
particularly as to the forms that I w^nt to speak this morn-
ing.
(At this point the room was darkened and the stereop-
ticon prepared for throwing the various photographs of
micro-organisms upon the screen.)
This illustration now on the screen is of the staphylococ-
cus pyogenes (Fig. i), or the pus-forming fungi that we most
frequently meet in abscesses. Almost every abscess that we

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