GLANDERS BACILLUS. 603 
southern countries, sometimes taking a mild course and 
remaining latent for a considerable time (Semmer and 
Babes). Apparently healthy horses, therefore, may pos- 
sibly spread the disease. 
Attenuation of virulence occurs in cultures which 
have been kept for some time, and inoculations with 
such cultures may give a negative result; or, when con- 
siderable quantities are injected, may produce a fatal 
result at a later date than is usual when small amounts 
of a recent culture are injected into susceptible animals. 
Several attempts have been made by investigators to 
produce artificial immunity against glanders, but so far 
with unsatisfactory results. According to Strauss, dogs 
may be protected by intravenous inoculations of small 
quantities of living bacilli against an injection with 
large quantities which usually kill them. Fenger has 
found that animals inoculated with glanders bacilli 
react less powerfully to fresh injections; and that rab- 
bits which have recovered from an injection of glanders 
are subsequently immune, the immunity lasting for from 
three to six weeks. Ladowski has obtained positive re- 
sults also in rabbits and cats by intravenous injections 
of sterilized cultures. Other observers have reported 
not only the production of immunity, but also cures, by 
the use of mallein. Mallein is produced by evaporat- 
ing a six-weeks’ old culture of the glanders bacillus in 
5 per cent. glycerin nutrient veal bouillon to 10 per 
cent. of its original bulk. It is made in the same way 
as Koch’s crude tuberculin from the tubercle bacillus 
cultures. 
Differential Diagnosis. It is often difficult to demon- 
strate microscopically the presence of the bacillus of 
glanders in the nodules which have undergone purulent 
