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INFLUENZA.                          447

poorly, except with such concentrated penetrating stains
as carbol-fuchsin and Loffler's alkaline methylene blue,
and even with these the bacilli stain more deeply at the
ends than in the middle, so that they appear not a little
like diplococci.

For the demonstration of the bacilli in the blood Canon
recommends a rather complicated method. The blood is
spread upon clean cover-glasses in the usual way, thor-
oughly dried, and then fixed by immersion in absolute
alcohol for five minutes. The stain which seems best is

Concentrated aqueous solution of methylene

blue,                                                        40;

0.5 per cent, solution of eosin in 70 per cent.

alcohol,                                                    20;

Distilled water,                                                40.

The cover-glasses are immersed in this solution, and kept
in the incubator for three to six hours, after which they
are washed in water, dried, and then mounted in Canada
balsam. By this method the erythrocytes are stained red,
the leucocytes blue, and the bacillus, which is also blue,
appears as a short rod or often as a dumb-bell.

Sometimes large numbers of the bacilli are present;
sometimes very few can be found after prolonged search.
They are often enclosed within the leucocytes. It really
is not necessary to pursue so tedious a staining method
for demonstrating the bacilli, for they stain quite well by
ordinary methods. They do not stain by Gram's method.

The bacillus is non-motile, and, so far as is known,
does not form spores. Its resisting powers are very re-
stricted, as it speedily succumbs to drying, and is cer-
tainly killed by an exposure to a temperature of 60° C.
for five minutes. It will not grow at'any temperature
below 28° C.

The bacillus does not grow in gelatin or upon ordinary
agar-agar. Upon glycerin agar-agar, after twenty-four
hours in the incubator, minute colorless, transparent,