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254 PATHOGENIC BACTERIA.
researches of J. H. Wrightl are in accord with those of
Tedeschi rather than with those of Baumgarteii, for
Wright observed first a marked degenerative effect upon
the tissue, and then an inflammatory exudation amount-
ing in some cases to actual suppuration.
As has been mentioned, cultures of the bacillus lose
their virulence more or less after four or five generations
in artificial media. While this is true, attempts to atten-
uate fresh cultures by heat, etc. have so far failed.
Leo has pointed out that white rats, which are immune
to the disease, may be made susceptible by feeding with
phloridzin and causing a glycosuria.
Kalning, Preusse, Pearson, and others have pre-
pared a substance, "mallein," from cultures of the
bacillus, and suggested its employment for diagnostic
purposes. It seems to be quite useful in veterinary
medicine, the reaction occasioned by its injection being
similar to that caused by the injection of tuberculin in
tuberculous patients. The manufacture of mallein is
not attended with great difficulty. The bacilli are grown
in glycerin bouillon for several weeks, killed by heat, the
culture filtered through porcelain and evaporated to one-
tenth of its volume. It has also been prepared from
potato cultures, which are said to produce a stronger
toxin, A febrile reaction of more than 1.5° C. following
the injection is said to be specific of the disease. Babes
has asserted that the injection of this toxic product into
susceptible animals will protect them from the disease.
Various experiments have been made with curative
objects in view. Certain observers claim to have seen
good results follow the injection of mallein in repeated
small doses. Others, as Chenot and Picq, find the blood-
serum from immune animals like the ox to be curative
when injected into infected guinea-pigs.
1 Jour, of Exp. Med,9 vol. L, No. 4, p. 577.