ANTHRAX GROUP 337 



original Pasteur method have been suggested, but in only slightly 

 modified form it is the one still most commonly used. 



Attempts to used killed cultures of anthrax bacilli or their 

 sterile products in producing immunity have failed to yield satis- 

 factory results in practice. Bail claims that an active immunity 

 may be established by the use of aggressins. The material used is 

 the serous fluid from animals dead from anthrax; this is sterilized 

 by phenol and injected into an animal to be immunized. The 

 aggressin should preferably be secured from the same species of 

 animal as the one to be immunized. The immunity is not estab- 

 lished until after the lapse of ten days or more. When established, 

 it is claimed that the animal will resist infection with fully virulent 

 cultures. This method of immunization with aggressins has not 

 been thoroughly tested out. 



Passive immunization by means of antisera has been tried by 

 numerous investigators. Cattle, the horse, ass, and sheep have 

 been used in the production of such sera. The animals are first 

 immunized by Pasteur's method of vaccination, and in ten days 

 or two weeks from TWIT t TO" f a 1P f a fully virulent culture 

 is injected. This is generally followed by a strong reaction. Two 

 or three weeks later a somewhat larger dose is given, and the dosage 

 is gradually increased until many loopfuls then entire cultures 

 are injected. In three to four months an immunity is developed 

 such that the subcutaneous injection of several cultures from agar 

 slants may be made without noteworthy reactions. The blood 

 is drawn about two weeks after the last injection. The animal 

 may -then, after the lapse of two weeks, be again injected and again 

 bled. The serum is pipetted off and preserved with 0.5 per cent, 

 phenol. Exact methods of standardization such as are used with 

 antitoxins cannot be employed. An approximation of the potency 

 can be reached by the intravenous injections of varying amounts 

 of serum into rabbits, and five to ten minutes later inoculating each 

 subcutaneously with y-^Vir of a loop of a virulent culture. A 

 serum is regarded as usable if two out of five animals injected with 

 2, 3, 4, 5, and 6 c.c. of the serum survive, and the remainder live 

 longer than control animals. As noted above, the immune serum 

 contains agglutinins, some bacteriolysins, and opsonins specific 

 for the anthrax bacilli. The serum may be used, both in prophy- 

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