BACILLUS MALLEI 4()o 
and not distinctive; no li(jiiefaction takes place. A uniform turbidity 
appears in l)roth after twenty-four hours' incubation at o7° (\, which 
gradually settles out as a tenacious, slimy sediment. If the culture is 
undisturbed, a pellicle gradually forms on the surface of the medium. 
Litmus milk is slowly acidified, and coagulation may occur after seven 
to fourteen days' incubation. Growth on old alkaline potato is dis- 
tinctive; after twenty-four to forty-eight hours' incubation a light 
brown, translucent layer appears, which has been likened in color and 
general appearance to a layer of honey. Later the growth becomes 
darker, even brownish-red in color, and the underlying potato becomes 
greenish or even brown. Potato that is acid in reaction does not exhibit 
the typical honey-yellow growth. 
The glanders bacillus is aerobic, facultatively anaerobic; the opti- 
mum temperature of development is 37° C, growth ceases above 43° 
C, and is extremely slow below 25° C. The resistance of the organism 
to chemical agents is not great, but it remains viable for several weeks 
when dried in pus or blood and maintained in a cool, dark place. An 
exposure of naked bacilli to 55° C. for five to seven minutes kills the 
organism. 
Products of Qtxoyftla.. — Chemical. — ^. mallei is culturally inert in 
purely protein media: indol, skatol and other products of degradation 
of amino-acids are not produced. Acid, but no gas, is formed in 
glucose broth, and acid is produced in milk. 
Enzymes. — ISo enzymes have been demonstrated in cultures of B. 
mallei. 
ro.rin*.— Soluble toxins have not been isolated from growths of the 
glanders bacillus; the poison of the organism apparently belongs to 
the group of the endotoxins. A substance analogous to tuberculin 
has been prepared from four to five weeks' glycerin broth cultures 
of B. mallei, called mallein or monin. The preparation of mallein 
is essentially the same as for tuberculin. The injection of mallein 
in moderate doses into normal animals may lead to transient fever and 
a slight local swelling w^hich quickly subsides. In horses infected with 
B. mallei a swelling appears within a few hours which is painful and 
inflamed; it gradually enlarges for twenty-four hours or more, and the 
lymphatics of the area usually become prominent. The swelling may 
persist for several days, but gradually diminishes and usually disap- 
pears within ten days. The temperature rises with the local swelling 
and reaches a point 1° to 2° or even 3° above the normal within twenty- 
four hours. The animal usually exliibits all the signs of a generalized 
reaction; it becomes listless, the coat roughens, and there is greater 
or lesser generalized weakness. The temperature usually persists for 
forty-eight hours or more. The reaction is specific but requires ex- 
perience for its interpretation. Variations in temperature are caused 
by strangles, bronchitis and other inflammatory infections, hence the 
temperature should be observed for some hours before the injection of 
the mallein. A positive reaction is of more diagnostic value than 
