HISTORIC DEVELOPMENT OF IMMUNOLOGY 19 



substances in the tissue fluids has been filled 

 with discoveries correlating both processes. 

 Largely through the researches of Wright and 

 Douglas, the presence of opsonins in certain 

 diseases has been taken as a measure (opsonic 

 index) of the resistance of the host, and a tech- 

 nic for detecting their presence and quantity in 

 the tissue fluids has been devised. This technic 

 and the information which it yields is of value 

 in some infections under certain limitations. 



Bordet has been a great pioneer in the theory 

 of serology and immunity reactions. He dis- 

 covered bacterial hemolysis (1898) and, with 

 Gengou, fixation of the complement (1900). He 

 also discovered with Gengou the specific bacil- 

 lus of whooping-cough (1906), the causal rela- 

 tion of which has been recently demonstrated 

 according to Koch's postulates by Mallory and 

 others (1913). Simon Flexner (1863-) has dis- 

 tinguished himself by his work on the etiology 

 and therapy of cerebrospinal meningitis (1906). 



Apart from the work of Bordet, Metchnikoff 

 and Ehrlich, there have been many advances in 

 serology of great practical value : notably, the 

 discovery of agglutination and its application 

 to the diagnosis of typhoid fever (1896) by 



