IMMUNITY IN TETANUS. 415 



depend on the short distance the toxin is obliged 

 to travel to reach the ganglionic cells. 



Although the toxin appears not to be taken up varieties of 



i JT < i r. f 1 T Tetanus. 



by the sensory nerves, a painful form of the dis- 

 ease, tetanus dolorosa (Meyer), may be pro- 

 duced experimentally by injecting the toxin into 

 the posterior roots of the spinal nerves. Koux 

 caused "cerebral tetanus" by introducing the toxin 

 into the cerebral tissue; the condition is charac- 

 terized by absence of contractures. "Local teta- 

 nus," in which the muscles in the vicinity of infec- 

 tion or inoculation are involved in contractures, is 

 the first, symptom of tetanus in experiment ani- 

 mals; it rarely occurs in man except in head teta- 

 nus. The phenomenon depends on the fact that 

 the toxin, being transmitted through the motor 

 nerves, reaches first the ganglionic cells which cor- 

 respond to the infected area. 



According to Metchnikoff, the only natural im- immunity 

 munity which man possesses to tetanus is leuco- in Man * 

 cytic and this may be sufficient to protect under 

 favorable conditions. The observations of Vaillard 

 and Eouget (cited above) support this claim. Sus- 

 ceptibility depends not only on the presence of 

 suitable receptors in the nervous tissue, but also 

 on the degree of affinity which exists between 

 these receptors and the toxin. In man and some 

 animals this affinity is very great, whereas in fowls 

 it is weak and an enormous amount of toxin is re- 

 quired to cause tetanus. A further proof of this 

 weak affinity in non-susceptible animals rests in 

 the fact that the toxin when injected into the blood 

 remains unabsorbed for a long time, whereas in 

 susceptible animals it disappears very quickly. Ac- 



