IMMUNITY, IMMUNIZATION, AND CURE. 69 



toxication. In contradistinction from this cellular hypothe- 

 sis is the chemic view of Behring and Ehrlich : that toxin 

 and antitoxin undergo a sort of double combination, which 

 proves innocuous for the tissues. The decision of this ques- 

 tion appears finally to have been made in favor of the 

 chemic theory by the more recent investigations of Ehrlich 

 with regard to ricin and antiricin. Ricin has the property 

 of causing the red blood-corpuscles in defibrinated blood to 

 collect together and to be precipitated to the bottom of the 

 vessel a process from which vital processes may with cer- 

 tainty be excluded. Ehrlich showed, then, that antiricin, 

 which is present in the blood-serum of animals immunized 

 to ricin, abolishes the activity of ricin in the test-tube, and 

 that the peculiar coagulation following the addition of ricin- 

 serum no longer takes place. Ricin and antiricin must, in 

 this instance, have directly influenced each other chemic- 

 ally. Ehrlich was further able to demonstrate that the 

 combination of toxin and antitoxin takes place much more 

 quickly in concentrated than in dilute solutions, that heat 

 hastens and cold retards its occurrence. As similar mani- 

 festations are observed in chemistry in the formation of 

 double salts, it would seem probable, according to Ehrlich, 

 that also the neutralization of toxins by antitoxins repre- 

 sents the formation of a double salt. 



The immunization of mammals against toxins is always 

 attended with febrile reaction, and it, therefore, appeared 

 that the formation of an antitoxin would not be possible in 

 the absence of fever. Metschnikoff, however, found that 

 of all animals the crocodile produces antitoxin most abund- 

 antly and most speedily, in spite of the fact that febrile 

 movement does not take place. 



According to the investigations of Behring and his col- 

 laborators, the antitoxin distributes itself throughout the 

 organism in man and in animals in such a manner that after 

 absorption of the injected serum, after passive immuniza- 

 tion, the blood to a certain extent extracts the antitoxin 

 from the tissues and stores it up. Twenty-four hours after 

 subcutaneous injection of serum, and in a shorter time after 

 intravenous or intraperitoneal injection, the maximum 

 amount of antitoxin in the blood is demonstrable. The 

 antitoxin is absorbed from stomach and bowel only when 

 lesions of the mucous membrane exist. The maximum 

 content of antitoxin in the blood persists for several days. 



