TOXINS AND ANTITOXINS 293 



fection with the Armstrong vaeeine virus. This virus is uni- 

 formly fatal to normal rabbits. When administered before or at 

 the time of infection, the animals are protected, but the serum 

 is ineffective after the virus is once established within the tissues 

 of the body. 



Tetanus. — Tetanus is a disease of great antiquity. The causal 

 relationship of CI. tetani to the disease was established by Kitasato 

 in 1889. Specific antitoxins were produced by Behring and 

 Kitasato in 1890. The organisms arc present in the intestinal 

 contents of most wanii-])loodod animals, iiicliuling man, and hence 

 have a wide dis1ril)iition in nature. They possess little or no in- 

 vasive power and gain entrance to the tissues through mechanical 

 injury. Once within the tissues they cannot esta])lish tliemselves 

 unless anaerobic conditions prevail. It is generally agreed that 

 they remain localized at the point of entry, multiply to a certain 

 extent, and secrete two soluble toxins; one is hemolytic and the 

 other brings about the characteristic symptoms of tetanus. While 

 there are several serological types, all tetanus bacilli produce 

 the same toxin. 



It is generally accepted that local tetanus and general tetanus 

 are both due to the action of the toxin on nerve cells in the cord 

 and brain. As to how the toxin reaches the cord and brain there 

 are three variants of a neural transport theory. According to 

 one, the toxin is transported in the nerve fibrils or axones of the 

 motor nerves by some process of "protoplasmic streaming." A 

 second explanation that is widely accepted assumes that the 

 toxin reaches the central nervous system along the endo- or 

 perineural lymphatic vessels of the motor nerves. According to 

 a third theory, the toxin is conveyed to the central nervous sys- 

 tem in the tissue spaces of the nerves. 



Reason for Ineffectiveness of Tetanus Antitoxin in Treat- 

 ment. — In previous chapters the units of tetanus toxin and anti- 

 toxin are given. Evidence is also offered which shows that tetanus 

 antitoxin is of definite value in preventing the disease. In the 

 treatment of general tetanus, large doses of antitoxin are admin- 

 istered. While the antibodies neutralize the circulating toxin, it 

 appears from statistical studies that such treatment does not 

 materiallv affect the outcome of the disease. When symptoms of 



