IMMUNITY AND SUSCEPTIBILITY. 119 



simultaneously with them. The first to observe this 

 seems to have been Wassermann and Takaki, 1 who found 

 that when a portion of the spinal cord of a rabbit was 

 crushed and suspended in a physiologic salt solution it 

 would, when mixed with tetanus toxin, protect the rab- 

 bit. This observation has been abundantly confirmed, and 

 is all the more remarkable because the reaction does not 

 seem to take place in vitro, but in corporo, for Wasser- 

 mann found that if the nervous substance was injected 

 twenty-four hours before the toxin or several hours after 

 it, or into another part of the body, it still exerted the 

 protection, acting like antitoxin. Marie 2 denies this in 

 part, and asserts that contact between the nervous sub- 

 stance and toxin is essential, for if the nervous substance 

 is introduced at one part of the body and the toxin injec- 

 tion made at some remote part, as, for example, into a paw, 

 the animals always die. Marie also observed that the 

 gray matter of the cerebral cortex contained the greatest 

 amount of toxin-destroying energy. 



MetschnikofT 3 has also confirmed the protective effect 

 of the comminuted brain substance, but does not agree 

 with Wassermann in all particulars. Thu#, instead of 

 looking upon it as an antitoxic effect, MetschnikofT views 

 it as an inflammatory reaction by which the pulverized brain 

 substance, being chemotactic, causes the accumulation of 

 large numbers of leukocytes at the seat of injection, which 

 are in all probability responsible for the toxin destruction. 



MetschnikofT observed that the brains of rabbits suffer- 

 ing from tetanus exerted no protective effect. This 

 observation will become more important when the subject 

 of Wassermann's theory of immunity is reached later on. 

 In order for the brain substance to exert its effect it must be 

 removed from the animal and crushed. To inject tetanus 

 toxin into the living brain is invariably to cause tetanus, 

 but to remove the brain and crush it and mix it with the 

 toxin is to destroy the toxin. MetschnikofT, however, 



1 Berliner klin. Wochenschrift, Jan. 3, 1898. 



* Annates de F Inst. Pasteur, 1898, No. 2. 3 Ibid. 



