1 8 DAVID J. DAVIS 



phenomenon in connection with his B. pertussis Eppendorf. It is well 

 known that influenza bacilli will live and develop through several 

 generations on non-hemoglobin media, when grown in mixed culture. 

 Pfeiffer, before he discovered the use of hemoglobin for influenza 

 culture, noted the growth of influenza bacilli on agar smeared with 

 sputum, but could not successfully transplant them on this medium 

 in pure culture. M. Neisser 1 obtained mixed cultures of B. xerosis 

 and B. influenzae from conjunctivitis in measles, and grew them 

 through 20 generations on plain agar. Strains of hemophilous bacilli 

 from throats of whooping-cough, measles, and scarlet fever were 

 in like manner carried through many generations in mixed culture. 

 With dead B. xerosis or its extracts, no growth occurred. He says 

 the presence of a living organism is necessary to produce this sym- 

 biotic effect. 



Various attempts have been made to explain the mechanism of 

 symbiosis. Ghon and Preyss 2 think it may be due to a reduction 

 of the hemoglobin or hematin by some substance produced by the 

 foreign organisms, thereby rendering the iron more available. Luers- 

 sen 3 found the favorable substance residing in the cell body of the 

 bacteria, and not in any product. He also claimed that nitrates, 

 made after several days' growth, were favorable for the development 

 of the influenza bacillus. 



Frequently, in the blood-agar plates inoculated from the whooping- 

 cough sputum, there was observed a conspicuous cluster of influenza- 

 like colonies surrounding other colonies present on the plates, such 

 as those of streptococcus, staphylococcus, and pneumococcus. They 

 were, in this location, not only larger, but apparently more numerous, 

 than when farther away from the foreign colonies. In order to 

 obtain such an arrangement, it seems necessary to have a large 

 number of influenza colonies in the plate, and a few of the foreign 

 organisms. When the former colonies are numerous, they are often 

 so small that a hand lens is necessary to see them; but around the 

 foreign colonies, as a result of some favorable influence, they become 

 much larger and are more easily visible. This appearance may 

 be easily obtained by sowing a blood-agar plate densely with the 



1 Deutsche med. t Wchnschr., 1003, 29, p. 462. ' Ibid., p. 434. 



Centralbl. /. Bakt., Abt. I, Orig. 1904, 35, p. 531. 



