108 THE ACUTE SELF-LIMITED INFECTIONS 



Tetanus Antitoxin. The toxin of the tetanus bacillus 

 is one of the most virulent poisons known. For ex- 

 ample, Trnmnnnr cubic centimeter or e^oVor minim 

 has been known to kill a mouse. -It is composed 

 of two parts, one the major, with a primary irri- 

 tating and secondary paralyzing effect on the cen- 

 tral nervous system, and a minor part having a 

 solvent action upon the red blood cells. These poisons 

 develop both in wounds and on laboratory culture 

 media. The methods for procuring this poison are 

 essentially those described under diphtheria, and 

 similar methods are used to immunize horses against 

 it. The antitoxin is in the immunized horse's serum, 

 and is refined and used in the same general manner as 

 diphtheria antitoxin. The unit in this case is the quan- 

 tity of antitoxin necessary to neutralize 1000 times the 

 smallest dose of toxin required to kill a guinea-pig 

 weighing 350 grams, llf ounces. The conditions of 

 administering antitoxin for tetanus are somewhat dif- 

 ferent from those in diphtheria. In the latter the poison 

 is largely circulating in the blood, while in tetanus some 

 of it is at the point of infection, some in the muscles and 

 nerves and central nervous system, and the least part is 

 in the blood. To reach all of these places it is necessary 

 to make injections into the vein and under the skin 

 as well. The surgeon attempts to reach those parts 

 first which have been affected the longest, to halt at 

 once any further damage there, and therefore methods 

 of treatment vary. Antitoxin is sometimes injected 

 directly into the nerves in order that some may neu- 

 tralize what toxin is remaining in them along their 

 length or in their muscle distribution. 



