106 VACCINE AND SERUM THERAPY. 



as those due to Bright 's disease. Practioners are undoubtedly 

 largely responsible for the misconceptions of laymen concerning 

 the effects of diphtheria anti-toxin injections. As a result of these 

 misconceptions frequently consent to use diphtheria anti-toxin, 

 when it is definitely indicated, cannot be obtained, and yearly 

 numbers of children whose lives could undoubtedly have been 

 saved are carried to the grave. 



TETANUS ANTI-TOXIN. 



In 1890, Behring and Kitasato immunized mice and rabbits 

 to tetanus by injecting cultures of the bacillus of tetanus. These 

 investigators found that blood from rabbits immunized to tetanus 

 bacilli, is able to protect mice against tetanus. The first reliable 

 anti -tetanic serum to be used in man, was put onto the market 

 in 1896. 



The process of producing anti-tetanic serum, is similar to that 

 employed to produce anti-diphtheria serum blood is drawn from 

 horses that have received injection of increasing amounts of tetanus 

 toxin. The toxin injected is produced by growing the tetanus bacillus 

 on bouillon. After ten to fifteen days of incubation under anaerobic 

 conditions, the bouillon culture is filtered through a Berkefeld filter. 

 The germ free filtrate contains the toxin, which is present usually in 

 large amounts. At the first injection into the horse usually one-half 

 c. c. of toxic bouillon, together with anti-tetanic serum are in- 

 jected. The amount of 'toxin is increased at each injection, until 

 finally seven hundred to eight hundred c. c. of toxin are tolerated 

 when given in one injection. After the third injection the anti- 

 tetanic serum is usually omitted. After several months of treat- 

 ment, and complete recovery from the last injection, the horses 

 are bled and the serum is collected. The serum is then concen- 

 trated and refined after the same methods that ar^e used for diph- 

 theria anti -toxin. 



The standardization of tetanus anti-toxin until very recently 

 has been indefinite and unsatisfactory. At the present time 

 different standards exist in the various countries. The unit of 

 anti -toxin for tetanus for the United States has been fixed as that 

 amount of tetanus anti -toxin that will protect a 350 gram guinea 

 pig for ninety-six hours against one thousand times the smallest 

 fatal dose of tetanus toxin. In order that the standard may be 



