ANTITOXINS^ANTIENZYMES 259 



toxins have been prepared experimentally for a large number 

 of both animal and vegetable poisons, including a number for 

 bacterial toxins. The only ones which, as yet, are of much 

 practical importance are antivenin for snake poison (not 

 a true toxin, however, see page 272), antipollenin (supposed 

 to be for the toxin of hay fever) and the antitoxins for the 

 true bacterial toxins of Corynebaderium diphthericB and 

 Clostridium tetani. Antitoxins for the two types, A and B, 

 of the toxins of Clostridium botulinum have been prepared 

 and tried out in some few cases of human food poisoning, 

 but unfortunately they have been used too late to be of much 

 value. In experiments with animals they have been showTi 

 to be as specific as other antitoxins. 



The method of preparing antitoxins is essentially the same 

 in all cases, though differing in minor details. For com- 

 mercial purposes large animals are selected, usually horses, so 

 that the yield of serum may be large. The animals must, of 

 course, be vigorous, free from all infectious disease. The 

 first injection given is either a relatively small amount of a 

 solution of toxin or of a mixture of toxin and antitoxin. 

 The animal shows more or less reaction, increased temper- 

 ature, pulse and respiration and frequently an edema at the 

 point of injection, unless this is made intravenously. After 

 several days to a week or more, when the animal has recov- 

 ered from the first injection, a second stronger dose is given, 

 usually with less reaction. Increasingly large doses are 

 given at proper intervals until the animal may take several 

 hundred times the amount which would have been fatal if 

 given at first. The process of immunizing a horse for diph- 

 theria or tetanus toxin usually takes several months. Varia- 

 tions in time and in yield of antitoxin are individual and 

 not predictable in any given case. 



After several injections a few hundred cubic centimeters 

 of blood are withdrawn from the jugular vein and serum 

 from this is tested for the amount of antitoxin it contains. 

 When the amount is found sufficiently large (250 "units" 

 at least for diphtheria per cc)^ then the maximum amount 

 of blood is collected from the jugular with sterile trocar and 



1 If the antitoxin is later concentrated (see last paragraph in this chapter) a 

 serum containing as little as 175 units per cc may be commercially profitable. 



