468 INFECTION AND RESISTANCE 



poison contains hardly any neurotoxin. Antitoxins may be produced 

 by the gradual immunization of horses, and have been produced in 

 this way by Calmette in the Pasteur Institute of Lille for some 

 years. Calmette standardizes his antitoxin by determining the 

 amount of serum which completely neutralizes in vitro 0.0001 gm. 

 of the poison as tested upon white light. He also determines the 

 protective power by injecting a rabbit with 2 c. c. of the serum and 

 two hours later gives 1 gm. of the poison. 



Noguchi has studied rattlesnake poison particularly and suc- 

 ceeded in preparing a strong antitoxin by the gradual immunization 

 of a goat. Great difficulty has always been experienced in attempts 

 at immunization with rattlesnake poison because of the very violent 

 local injury produced by injections of the venom. The potency of 

 the serum produced by him was such that 2% c. c. of goat serum 

 protected guinea pigs against 12 times the fatal dose of rattlesnake 

 poison if given at the same time. If the antivenin was given one 

 hour later, 5 times the amount of serum had to be given. 



PASSIVE IMMUNIZATION IN DISEASES CAUSED BY BAC- 

 TERIA WHICH DO NOT FORM SOLUBLE TOXINS 



As we have stated in another place the greatest therapeutic suc- 

 cesses with passive immunization have been achieved in bacterial 

 diseases in which the malady is essentially a toxemia due to a soluble 

 toxin. In such cases the serum of actively immunized animals con- 

 tains specific antitoxins by virtue of which the toxins circulating in 

 the blood of the patient are directly neutralized, quantity for quan- 

 tity, with consequent therapeutic benefit. In the case of bacteria in 

 which no toxins are formed, the immunization of an animal is not 

 followed by the formation of any poison-neutralizing principle. 

 Here the injection of bacteria, dead or alive, or the invasion of the 

 bacteria in the course of spontaneous disease, is followed by the 

 formation of specific antibacterial substances, lytic, opsonic, agglu- 

 tinating, or precipitating bodies, the nature of which we have dis- 

 cussed in other chapters. The toxemia which occurs in such cases 

 is due as we have seen to derivatives of the bacterial protein which 

 by some observers are regarded as preformed endocellular poisons 

 liberated by the lytic action of the serum, and by others as split 

 products of the bacterial protein, non-existent until the bacterial cell 

 has been acted upon by the serum components and destroyed. How- 

 ever this may be, the recovery from diseases of this nature is accom- 

 plished by bacterial destruction ; this may be direct, by the bacteri- 

 cidal action of the serum, or indirect by opsonic properties which 

 induce phagocytosis. The poisons w r hich are liberated from the bac- 

 terial bodies, if free, can do their injury, and no neutralizing sub- 



