Page 72 - My FlipBook

cut in the infirmary has this form of micro-organism. There ;
are four species of this form, all pus-forming organisms, and
there is another that is in some question, and that particu-
lar one we find almost continually in the human mouth.
This, as we see it in specimens prepared from gelatin or agar
cultures, is a simple, round cell. Now, here are two joined
together, and here are two which are just dividing. All
of these forms of micro-organisms multiply by fission, i. e.,
one cell divides into two. There is never a mother cell.
For instance, this cell divides and we have two young cells
we have nothing left, no mother cell. Most of the micro-
organisms divide upon a particular pole. The earth is said
to be round, and yet we speak of its poles. These micro-
organisms are round, and yet we speak of their poles just in
the same sense that we speak of the poles of the earth. They
divide, then, most of them, upon one pole. Now, for in-
stance, here is a round one here ; in its growth it will elon-
gate upon one pole and then divide upon the equator, form-
ing two round cells. Then each of these will elongate and
divide again, forming two more round cells, and so on con-
tinuously during their growth. So that in almost all of the
coccus forms we get these forms of twos that you see so fre-
quently over this screen.
I want to say a word about the size of these, (scale is
flashed upon the screen), by comparison with a scale. This
is a picture of a micrometer scale that is cut upon glass for
use upon the stage of the microscope. We lay an object
upon this and measure it. This is one millimeter from end
to end (indicating), divided into lOO parts ; i. e., each of these
lines is one one-hundredth of a millimeter. Now this picture
of micro-organisms is taken with the twelfth-inch lens, while
this picture of the scale is taken with a two-thirds. Now we
will remove this picture of the scale and place one in that
is taken with the sixth-inch lens (screen). I want you to
notice this particularly and see if you can conceive of the
minuteness of these organisms. Now here is the same scale
taken with the sixth-inch lens, and you see the lines are very
much more divided than they were before. Now we will put
in the one that is taken with the twelfth-inch lens, the same
lens with which this picture of the micro-organisms was
made, and at the same focal distance (screen). Now you

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