FORMATION OF ANTITOXINS 225 



induced experimentally, while the animals became more and more im- 

 mune, virulent bacilli may, nevertheless, be present at the site of in- 

 jection. Here, then, was an example of immunity that could not be 

 explained on the basis of bacteriolysis. Later, in 1890 and 1892, Behr- 

 ing, in collaboration with Kitasato and Wernicke, made further im- 

 portant discoveries, showing that the blood-serum of animals actively 

 immunized against diphtheria and tetanus would protect normal animals 

 against these diseases, and, furthermore, that the blood-serum of the 

 immune animals did not possess bactericidal properties. These ob- 

 servers also demonstrated that such serum could be used therapeutically 

 for the cure of an infection already in progress. 



Soon after these discoveries Ehrlich showed that specific antitoxins 

 (antiricin, antiabrin, etc.) could also be produced against the poisons 

 of some plants, and Calmette produced a similar antitoxin (antivenin) 

 against snake poison. Other observers since then have increased the list 

 of poisons against which antitoxins can be produced; as, for example, 

 Kempner has produced an antitoxin against the poison of Bacillus botu- 

 linus, and Wassermann one against that of Bacillus pyocyaneus. 



Formation of Antitoxins. It was formerly believed that there was a 

 direct conversion of toxin into antitoxin, but this certainly is not the 

 case, for the amount of antitoxin produced is altogether out of propor- 

 tion to the amount of toxin injected. 



Antitoxins are formed by those cells that anchor the toxins. In 

 order to produce them it is necessary that the toxin enter into direct 

 union with the cells and exert a stimulating influence on them, for where 

 a loose union occurs, as between cells and alkaloids, antibodies are not 

 formed. 



Having entered into chemical union with the side-arms of cells, 

 a toxin may destroy the entire cell, and if a sufficient number of 

 these are destroyed, the host will show symptoms of infection and may 

 succumb. If, however, the cell itself is not destroyed, but only one or 

 more of the side-arms injured, the damage is repaired by the cell form- 

 ing new side-arms that have a specific affinity for the toxin responsible 

 for their production. According to Weigert's overproduction theory, 

 a cell once stimulated to produce these side-arms or receptors continues 

 to produce them for some time, even after the stimulus has been re- 

 moved. In this manner the specific receptors are produced in excess, 

 and since all cannot remain attached to the parent cell, the excess is 

 discharged into the blood-stream. Each of these cast-off receptors is 

 capable of uniting with toxin, thus neutralizing the poisonous principles 



15 



