136 VETERINARY BACTERIOLOGY 



is, therefore, not always the same as antitoxin immunity. This 

 hypersensitiveness is of unusual occurrence. An animal that is 

 being immunized against tetanus toxin by injections of increasing 

 amounts may suddenly and unexpectedly show a marked reaction, 

 or may even succumb, when additional amounts are injected, 

 even though antitoxin may be demonstrated in considerable 

 quantities in the blood. It is evident that, although this phe- 

 nomenon is of infrequent occurrence, it is of some little importance. 

 Possibly this may be related to the reactions to be described later 

 under the heading of Anaphylaxis. 



Antitoxins of Commercial Importance. Antitoxins specific 

 for the venom of certain snakes and for diphtheria and tetanus 

 toxins are prepared commercially. The manufacture and 

 standardization of these antitoxins are of importance to the 

 veterinarian for several reasons. The theory of immunity has 

 been largely developed through a study of diphtheria toxins and 

 antitoxins. The larger animals, such as the horse and goat, are 

 generally used in the commercial manufacture of antitoxin. 

 The tetanus antitoxin is used extensively in veterinary practice. 

 A brief consideration of the production of diphtheria and tetanus 

 toxin and antitoxin is, therefore, advisable. 



Manufacture of Diphtheria Toxin and Antitoxin. Diphtheria 

 toxin is prepared by growing the diphtheria bacillus in suitable 

 broth. A sugar-free broth is prepared as described in Chapter 

 VII. This is titrated and the reaction adjusted accurately to 

 +0.5. It is then placed in flat-bottomed toxin flasks in a layer a 

 few centimeters in thickness, and autoclaved. To each flask is then 

 added sufficient sterile dextrose solution to make a 0.2 per cent, 

 dextrose broth. It is found in experience that different strains of 

 the diphtheria bacilli may vary considerably in toxin production. 

 The strain used most frequently in the United States is the one 

 known as the Park-Williams. The organism is grown in broth 

 tubes, where it forms a film over the surface. Portions of this film 

 are transferred carefully to the surface of the broth in the flasks and 

 incubated at 37 for eight days. Microscopic examination of the 

 culture should show it to be uncontaminated. To destroy the 

 bacteria and prevent possible infection of those handling the 

 material 5 c.c. of phenol or similar antiseptic is then added to 



