CHAPTER III 



THE PHENOMENA OF ANTITOXIN 

 FORMATION 



As a general rule, to which there are important exceptions, it is 

 necessary to make use of susceptible animals for the production 

 of antitoxin. When toxin is injected into animals in which it pro- 

 duces no injurious effects, it either disappears rapidly from the 

 blood or remains for a long time in that fluid or in the tissues 

 without leading to the formation of antitoxin. The most remark- 

 able exception to this rule is the way the cayman reacts to tetanus 

 toxin. The animal is immune, and if kept in the cold (20 C.) the 

 toxin soon disappears from the blood, no antitoxin being formed. If, 

 however, it is kept at an elevated temperature (32 to 37 C.), the 

 toxin disappears as before, but now antitoxin makes its appearance 

 (Metchnikoff). Such cases are exceptional, and when we wish 

 to procure antitoxin, we make use of an animal in which the 

 toxin in question produces symptoms of intoxication. The pro- 

 cess is usually much easier in large animals, such as horses or 

 goats, than in small ones, such as rabbits or guinea-pigs, the 

 immunization of which presents considerable difficulties. We 

 shall take as illustrations of the general phenomena of the pro- 

 cess the methods adopted for procuring diphtheria antitoxin and 

 tetanus antitoxin from horses, since these have become so familiar 

 from their extensive application. 



On injecting a small dose of a potent diphtheria toxin sub- 

 cutaneously into a horse say, \ c.c. under the skin of the 

 neck we find there is a latent interval of a few hours or a 

 day before the development of symptoms ; then there is a local 

 reaction, consisting in the formation of a hard brawny mass of 

 inflammatory oedema round the site of the inoculation, and a 

 general reaction, consisting in fever, anorexia, and symptoms of 

 general malaise. These symptoms last a day or two, according 

 to the dose of toxin injected, its potency, and the degree of sus- 



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