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*286                 PATHOGENIC BACTERIA.

that a temperature of 58░ C. for ten minutes is fatal to it.
Notwithstanding this susceptibility, the organism can
be kept alive for several weeks after being dried upon
shreds of silk or when surrounded by dried diphtheria
membrane.

No flagella have been demonstrated upon the bacillus.
It is non-motile.

Fernbach has shown that when the organisms are
grown in a medium exposed to a passing current of air,
the luxuriance of their development is increased, though
their life-cycle is shorter. The growth can also take
place when the air is excluded, so that the bacillus must
be classed among the optional anaerobic organisms.

The diphtheria bacillus grows readily upon all the
ordinary media, and is a very easy organism to obtain
in pure culture. Loffler has shown that the addition
of a small amount of glucose to the culture-medium
increases the rapidity of the growth, and suggests a
special medium which bears his nameŚLoffler's blood-
serum mixture:

Blood-serum,                                                3;

Ordinary bouillon + i per cent, of glucose,    i.

This mixture is filled into tubes, coagulated, and steril-
ized like blood-serum, and is one of the best-known media
in connection with the study of diphtheria.

The studies of Michel1 have shown that the develop-
ment of the culture is much more luxuriant and rapid
when horse serum instead of beef or calves' blood is used.
Horse's blood can easily be secured by the introduction of
a trocar into the jugular vein ; 5 liters of it can be with-
drawn without causing the animal any inconvenience or
producing symptoms.

The impossibility of clinically making an accurate di-
agnosis of diphtheria without a bacteriologic examination
has caused many private physicians and many medical
societies and boards of health to equip laboratories where

1 Centralbl.f. Bakt. u. Parasitenk., Sept. 24, 1897, Bd. xxii., Nos. loand II.