366 COLLECTED STUDIES IN IMMUNITY. 



exist between the toxin introduced and the resulting antitoxin. 

 Knorr, for example, has shown that the injection of tetanus toxin into 

 a horse is followed by the production of an amount of antitoxin which 

 would neutralize 100,000 times the dose ot poison employed. Such 

 an enormous disproportion cannot be reconciled with Buchner's view, 

 according to which each part of toxin would make an antitoxin 

 equivalent. This ratio can be explained only by a theory which 

 makes the production of antibody more independent of the exciting 

 agent. 



Another fact, which cannot be reconciled with a transformation 

 of toxin into antitoxin, is the marked difference existing between 

 so-called active and passive immunity. If, for example, by injecting 

 an animal with poisons or bacteria an active immunity is produced, 

 this immunity may in favorable cases persist for years, while 

 in passive immunity the preformed antitoxin introduced into the 

 organism exists but a short time. Such a difference could not exist 

 if the antitoxin were nothing else than transformed toxin; for in 

 that case it should be absolutely immaterial how the antitoxin now 

 in the organism had originated. The difference, however, depends 

 on the fact that in active immunity the tissues of the body con- 

 stantly produce new antitoxin, keeping pace with the excretion of 

 the same. 



This production of the antitoxin by the body-cells is further- 

 more confirmed by the interesting experiments of Roux and Vaillard, 

 and of Salomonsen and Madsen. They took an animal which had 

 been actively immunized, and whose serum showed a constant amount 

 of antitoxin, and by means of repeated venesection abstracted a 

 considerable portion of its blood. In case the antitoxin had been 

 derived from the toxin introduced there should, now that the last 

 traces of poison had disappeared from the body, have been a marked 

 loss of antitoxin from the blood. On the contrary within a short 

 time it was found that the amount of antitoxin had again reached 

 its previous level. Another point in support of the assumption that 

 the body-cells produce the antitoxin is an experiment of Salomonsen 

 and Madsen, which shows that the amount of antitoxin present in the 

 blood of an actively immunized animal is increased if the animal is 

 treated with substances which increase the secretion of blood- cells 

 in general, e.g. pilocarpine. This experiment was advanced by 

 Salomonsen and Madsen as absolutely opposed to the transformation 

 hypothesis and supporting their secretion theory. 



