126 ANTITOXINS. 



of its antitoxic power. When taken by mouth, the anti- 

 toxins are digested in the alimentary canal, because of their 

 proteid composition, without, however, conferring immunity. 

 It is impossible to obtain antitoxin in a pure form. 



Specific action of antitoxin : The action of certain antitox- 

 ins is specific. The diphtheria antitoxin protects against the 

 diphtheria bacillus and its toxin only. Hueppe claims that 

 specific antitoxins also protect against other infections, 

 although in a less degree. Antitoxins, as a rule, are effective 

 only against the toxin and not the germ as well, unless the 

 immunization has been produced by the use of active cultures 

 of the germ. The action of the antitoxin may be due to a 

 direct chemical combination with the toxin, forming an inert 

 mixture ; or indirectly by a stimulation of the activity of the 

 tissue-cells by the antitoxin. It may also act through a com- 

 bination of the antitoxin with the toxin through the medium 

 of the combining substances or ferments in the blood. 



Manufacture : Antitoxin is now being manufactured on a 

 large scale for the purpose of producing artificial immunity 

 against certain infectious diseases, and also for use as a 

 therapeutic agent. The method consists in immunizing large 

 animals, principally horses, by huge quantities of toxin, and 

 then withdrawing a certain quantity of blood when the 

 desired degree of immunity has been attained. The prepara- 

 tion of the specific antitoxins will be considered in the chap- 

 ters on the infectious diseases. 



The exact strength of the serum must be determined before 

 it can be used either for immunizing purposes or therapeuti- 

 cally. The amount of antitoxin required to protect 25,000 

 grams weight of guinea-pigs from the minimal fatal dose of 

 toxin is called an immunizing unit. Usually from 600 to 

 1800 immunizing units are required to produce a cure. This 

 amount is contained in 2, 4, or 6 c.c. of commercially pre- 

 pared antitoxin. 



Method of administration : It is useless to administer anti- 

 toxins by mouth, because, as already mentioned, they are 

 digested * in the intestinal canal. Therefore they always 

 are administered by hypodermic injection into the subcu- 

 taneous tissues. It really does not matter where the injec- 



