Page 93 - My FlipBook

EIGHTH LECTURE.

Exhibition of Tubes Planted at Previous Lecture.

All of the tubes of broth which I planted on Monday
have grown very well. You will see in the bottom of the tubes
the micro-organisms that have grown and fallen down ; the
tubes are not quite clear. Within a few days they will all
settle to the bottom and the broth in the tube above will be
clear again. They have made their growth and formed their
waste product until they are choked and cease to grow.
Every tube has made a good growth. The one that had the
litmus has been almost decolorized. Quite frequently we get
a growth in litmus that decolorizes the litmus completely.
The little color that is left, you will notice, is red. In the
bottom of the tube there is only a yellowish coloring. If it
is shaken that will be destroyed. In a few of the tubes there
are still some micro-organisms hanging to the sides in
plaques ; these fall down very readily when the tubes are
shaken ; they do not adhere to the glass very closely. Seeing
that these would make their growth and fall down vesterday,
I planted two more tubes, hoping to have them in shape so
that the broth would look milky white, but they grow a little
too quickly for that. I planted them at about three o'clock
yesterday and they have already begun to fall down. Those
two tubes that have no papers on I planted yesterday. The
other two tubes that have papers, but no labels, were the
control tubes that I did not plant on Monday, that I have left
in the incubator with the others. You will see that they are
still perfectly clear. (Passes tubes to the class.)

Planting iVlJcro=organisms From the Saliva.

While you are looking at those I want to plant a few
tubes of agar agar and gelatin. With these I will use simply
a straight platinum needle, without any barbs or crooks or
loops. We usually make use of three forms of needles in
planting—the needle with the loop on the end, the straight
platinum needle and one with a hook on the end. The one
with a hook on the end is used almost exclusively in replanting
from plants that have been made previously in the tubes, pick-

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