ANTIRABIC SERUM 617 



occurs antibodies will be formed which prevent the organisms of the 

 street virus from producing an attack of hydrophobia. That there 

 is, indeed, a morphologic difference between the street virus and 

 the fixed virus is shown by the fact that the latter never produces the 

 large Negri bodies but only the smallest forms of them. 



Resistance. The rabies virus possesses a moderate resistance. 

 However, it must not be forgotten that the action of antiseptics, 

 etc., cannot be studied upon the pure virus, as it is always more 

 or less protected by the natural substances or body fluids in which 

 it is contained. In a tabulation by Heim, compiled from the work 

 of different authors, the following figures are given: The rabies virus 

 is destroyed by 1 to 1000 bichloride of mercury in two to three hours; 

 1 per cent, carbolic acid in two to three hours; 5 per cent, carbolic 

 acid, 5 per cent, salicylic acid, 10 per cent, sulphate of copper, 1 per 

 cent, kreolin in five minutes; 70 per cent alcohol in twenty-four 

 hours. Formalin vapors fifteen to forty-five minutes; gastric juice 

 after twenty-four hours; exposure to 45 C. in twenty-four hours; 

 50 C. in one hour; 52 to 58 C. one-half hour;- 60 C. very rapidly. 

 Low temperatures have no effect upon the virus. Frothingham found 

 the cord of a rabid dog kept at 40 C. virulent after one year and 

 ten months. The virus remains virulent longer in buried cadavers 

 than in those exposed to the air and light. Glycerin does not destroy 

 the virus, in fact, it acts as a conservative for it for months. 



Antirabic Serum. Babes and Lepp were the first to show, as early 

 as 1889, that the serum of dogs immunized by Pasteur's method 

 contained substances which are antagonistic to rabies virus, and, 

 therefore, can be used to neutralize it, and also, as is claimed, be 

 employed to protect dogs by passive immunization against inoculation 

 with fixed virus and against the bites of dogs suffering from hydro- 

 phobia. These early experiments of Babes and Lepp appear to have 

 been the first to demonstrate the formation of antibodies against a 

 virus, and of the employment of such antitoxin to produce what is 

 now universally known as passive immunization. However, the 

 claim that antirabic serum can cure hydrophobia after it has made 

 its appearance or can favorably modify its course is not admitted as 

 correct by Kraus. Babes and those who have used an antirabic 

 serum on man bitten by rabid animals have never used it alone but 

 always in combination with fixed virus. In other words, they have 

 used the simultaneous method, never the method of pure passive 

 immunization, and it is claimed that the results of the simultaneous 

 method have not been better than the uncombined treatment with 

 fixed virus. The antirabic serum of Babes is prepared by first treat- 

 ing rabbits, donkeys, dogs, and sheep by Pasteur's method and sub- 

 sequently injecting increasing, finally large, doses of fixed virus. The 

 blood of the hyperimmunized animals is drawn ten to twenty-five 

 days after the last injection of virus and the blood serum is obtained 

 in the same manner as in the case of diphtheria or tetanus antitoxin 



