188 A MANUAL OF BACTERIOLOGY 



are thrust off by the single injection of the non-poisonous 

 toxin, or toxoid, Wassermann ascribed to the lack of 

 stimulus which resides in the toxophore groups (see above). 



The slow combination of the haptophore and receptor 

 groups has been proved by Wassermann in another way. 

 The researches of Meyer and Ransom have shown that 

 tetanus toxin is absorbed by the nerve-trunks, not by 

 the blood and lymph-channels, while tetanus antitoxin 

 is absorbed by the latter the blood and lymph-channels. 

 Adrenalin is a substance which strongly contracts the 

 capillaries, and thus tends to block absorption in a par- 

 ticular area. The following experiment was devised : 

 Tetanus toxin and antitoxin were mixed in such propor- 

 tions that the mixture was innocuous to animals, i.e. it 

 was just neutral. If this mixture be injected into the 

 hind paw of a guinea-pig no tetanus develops. When, 

 however, some adrenalin is injected into the hind paw of 

 a similar-sized guinea-pig, and a few minutes are allowed 

 to elapse so that the capillaries may contract, and then 

 the mixture of toxin and antitoxin is injected, topical 

 tetanus ensues. The explanation of this is that the 

 channel of absorption for the tetanus antitoxin, the vessels, 

 is blocked by the adrenalin, while that for the toxin, the 

 nerve path, remains open. The toxin arid antitoxin had 

 not yet combined, or such combination as had occurred 

 was a loose one and became dissociated, and, therefore, 

 the toxin travelled along the nerves to the central nervous 

 system with the production of tetanus. 



The experiment, however, succeeds only within a certain 

 period, not exceeding an hour after mixture of the toxin 

 and antitoxin, because after this the toxin-antitoxin 

 combination becomes a stable one. 



If a longer time say three or four hours is allowed 

 to elapse, it will be found that, even in the adrenalin 

 animal, no tetanus is produced, because by this time the 



