124 CONTEMPORARY SCIENCE 



the prevention and sometimes in the treatment of dis- 

 ease, and so-called specific serum therapy. Moreover, 

 these studies have placed in the hands of the bacteriologist 

 a powerful instrument for detecting, through immunity 

 reactions carried out in test tubes, or the animal body, 

 new varieties of pathogenic or disease-producing bacteria 

 and of investigating more closely and sorting out groups 

 of pathogenic microbes not hitherto subject to analysis. 

 Finally, the immunity reactions, as they are generically 

 named, have been found not to be restricted to bacterial 

 cells and poisons, but to apply to a wide variety of cells 

 and their products. For it should be recalled that in the 

 decade immediately succeeding the discovery of antitoxin, 

 agglutinins, precipitins, bacteriolysins, cytotoxins, hemoly- 

 sins, complements, chemotaxis, anaphylaxis, and the 

 minutiae of phagocytosis were discovered and became the 

 objects of animated and of ten, feverish and sometimes con- 

 troversial but always profitable investigation. 



It happened also and quite naturally and logically that 

 this should be the heyday of hypotheses concerning the 

 biological basis of immunity and the manner in which in- 

 teraction takes place between toxin and antitoxin inside 

 as well as outside the body, and of the englobing of bac- 

 teria and other bodies by the blood and tissue cells, as 

 well as the nature of the combinations and permutations 

 and reactions between the more complex bacteria and 

 cells in course of their immunological transformations. 

 And thus there came to be elaborated the side-chain hy- 

 pothesis of Ehrlich, which vied with the phagocytic theory 

 of Metchnikoff as well as with the adsorption theory of 

 Bordet and the physico-chemical theory of Arrhenius. 

 And if in our busy lives of to-day we think less of re- 

 ceptors and amboceptors, of complements and complemen- 

 toids, haptophores, and toxophores, and limit ourselves 

 somewhat more closely, perhaps even a little too exclu- 

 sively, to the observed fact itself, yet it is well that we 

 do not forget how great at the time was the stimulus to 



