566 BACTERIOLOGY. 
opment outside of the body like anthrax. In the form 
of spores, however, reproduction may take place; and 
by contamination with these, through deep wounds ac- 
quired by animals in infected pastures, the disease is 
spread. Possibly also it may originate through infec- 
tion of the mouth and by feeding—which would account 
for the cases of symptomatic anthrax occurring in stall- 
fed cattle (Hafner). 
It is well known to veterinarians that recovery from 
one attack of symptomatic anthrax protects an animal 
against a second infection. Artificial immunity to in- 
fection can also be produced in various ways: by intra- 
venous inoculations; or, in guinea-pigs, by inoculations 
with bouillon cultures which have been kept for a few 
days and as a result have lost their original virulence, 
or with cultures kept in an incubating oven at a tem- 
perature of 42° to 43° C.; or by inoculations made into 
the extremity of the tail; or by inoculations with filtered 
cultures, or with cultures sterilized by heat. For the 
production of immunity in cattle, Arloing, Cornevin, 
and Thomas recommend the use of a dried powder of 
the muscles of animals which have succumbed to the 
disease, and which have been subjected to a suitable 
temperature to ensure attenuation of the virulence of 
the spores contained in it. Two vaccines are prepared, 
as in anthrax—a stronger vaccine by exposure of a por- 
tion of the powder to a temperature of 85° to 90° C, 
for six hours, and a weaker vaccine by exposure for the 
same time to a temperature of 100° to 104° C. Inocu- 
lations made with this attenuated virus (into the end of 
the tail)—the weakest first and later the stronger—give 
rise to a local reaction of moderate intensity, and the 
animal is subsequently immune from the effects of the 
