TETANUS. 151 



covery of this fact by Behring and Kitasato has been the open- 

 ing wedge to serum therapy. 



Tetanus antitoxin, like diphtheria antitoxin, is produced by 

 inoculating large animals, like the horse, with minute doses 

 of the toxin, diluted at first with Gram's iodine solution, and 

 artificially establishing in the horse an immunity against the 

 poison. The dose of the toxin is gradually increased, and 

 injected every few days into the animals until immense doses 

 (600 to 700 c.c.) may be injected at one time without pro- 

 ducing any marked symptoms. When immunity has thus 

 been secured, blood is taken from the animal and its serum 

 tested, when it is found to have decided powers of neutralizing 

 the toxin. 



Tetanus antitoxin is useful chiefly as a preventative against 

 tetanus, and in veterinary medicine has been found of great 

 value. When applied to the human subject, however, the 

 results have not been so satisfactory, for it is used then only 

 as a therapeutic agent. At the time of its employment the 

 symptoms of tetanus have generally shown themselves, and 

 these are exceedingly rapid and violent in their effects, and 

 commonly fatal. A number of observers have derived very 

 decided benefit from its use, however, especially by injecting 

 it into the ventricles of the brain, where it may act by directly 

 and locally combating the poisonous action of the tetanin 

 present. 



Tetanus antitoxin is measured somewhat differently than is 

 diphtheria antitoxin. Its strength is expressed as follows : 

 1 in 1,000,000 or I in 10,000,000. This means that 1 c.c. 

 of the antitoxin is capable of protecting from infection 

 1,000,000 or 10,000,000 grams of guinea-pig. In some 

 cases an antitoxin of 800,000,000-gram power has been 

 obtained. 



This antitoxin, however, does not retain its power very 

 long, and deteriorates quickly in the fluid form. It is gener- 

 ally made into a powder, which may be dissolved into a 

 neutral saline solution for use. 



