224 TEXT-BOOK OF BACTERIOLOGY. 



etc., the transmission takes place and the animals die of genuine 

 black-leg. 



As may be remembered, we have already pretty fully considered 

 these matters and have attempted to account for them. 



Artificial immunity from black-leg may be brought about with 

 extreme ease and in many different ways. First, it can be produced 

 in connection with attenuation. Kitasato rendered Guinea-pigs 

 non-susceptible with his bouillon cultures which had lost their viru- 

 lence; the bacteria bred at high temperatures produce the same 

 effect, and, as we have said, the inoculation of attenuated spores 

 works very successfully. It is the only method employed in real 

 practice, and, proceeding from Arloing and his collaborators, has 

 been perfected by Kitt. His process is as follows : Muscles of ani- 

 mals which have perished of black-leg are dried at 33° to 35° C. 

 and then divided into two parts. One part is kept for six hours 

 at a heat of 85° to 90° C, the other also for six hours, but at 100° 

 to 104° C. Thus one obtains a premier and a deuxieme vaccin ; the 

 powdered flesh is mixed with sterilized water or bouillon and in- 

 jected subcutaneously into the animals at suitable intervals. In 

 other cases — for instance, with cattle and sheep — the inoculation of 

 very small quantities of unaltered rod-cells suffices to produce a 

 local reaction which is also found to grant immunity. Further, the 

 ihoculation of the virus into parts of the body — the tip of the tail, for 

 instance — where it finds no suitable point of attack, proves success- 

 ful, as does also an injection direct into the blood-vessels, which 

 are unconnected with the subcutaneous tissue, the proper bed of 

 development for these bacteria. 



In the case of black-leg bacillus we see with special clearness 

 that it is the excretions which play the chief part in producing im- 

 munity. Eoux and Chamberland found that filtered cultures were 

 successful in causing it, and even granted to the Guinea-pig not 

 only an immunity from black-leg, but also from malignant oedema 

 — a fact, however, which Kitasato denies on the ground of some ex- 

 periments of his own. The last-named investigatoi- kept bouillon 

 cultures half an hour at 80° C, killing thereby the sporeless bac- 

 teria, and produced immunity with this material. 



As the protective inoculation against black-leg, if properly con- 

 ducted, is without danger and, at least as far as has yet been 

 observed, does not occasionally demand a victim (as in the case 

 with anthrax), and as, further, the immunity appears to be endur- 

 ing and reliable, the inoculation of cattle is unconditionallj' recom- 

 mended for actual practice, even by cautious practitioners. 



By microscopic examination, by breeding outside the animal 



