498 PATHOGENIC MICROORGANISMS 



Other .substances which, added to neutral or slightly alkalin 

 agar, have been used for the cultivation of influenza bacilli are the 

 yolk of eggs'" (not confirmed) and spermatic fluid. 27 None 1 of these, 

 however, are as useful as the blood media. Symbiosis with staphy- 

 lococci,- 8 too, has been found to create an environment favorable 

 for their development. 



Influenza bacilli do not grow at room temperature. Upon suit- 

 able, media at 37.5 C. colonies appear at the end of eighteen to 

 twenty-four hours, as minute, colorless, transparent droplets, not 

 unlike spots of moisture. These never become confluent. The limits 

 of growth are reached in two or three days. To keep the cultures 

 alive, tubes should be stored at room temperature and transplanta- 

 tions done at intervals not longer than four or five days. 



Biology. The bacillus is aerobic, growing in broth-blood mix- 

 tures only upon the surface, hardly at all in agar stab cultures, and 

 not at all under completely anaerobic conditions. 



As it does not form spores, it is exceedingly sensitive to neat, 

 desiccation, and disinfectants. Heating to 60 C. kills the bacilli 

 in a few minutes. In dried sputum they die within one or two 

 hours. They are easily killed even by the weaker antiseptics. Upon 

 culture media the bacilli, if not transplanted, die within a week or 

 less, the time depending to some extent upon the medium used. 



Toxin Formation. The opinion in former years has been that 

 the poisonous substances produced by the influenza bacillus were 

 in the nature of endotoxins and a great many observers noted toxic 

 symptoms on the injection of whole cultures into rabbits and guinea 

 pigs. There is no question about the fact that such cultures in 

 quantities of a cubic centimeter or more can exert powerful poison- 

 ous action. In our laboratory, Julia T. Parker 29 recently showed 

 that culture filtrates of young influenza bacilli would kill rabbits 

 in doses of from 1.5 c.c. upward. The best poisons are produced 

 by cultivating the organisms on broth of a P H of 7.8, with 5 to 10 

 per cent defibrinated rabbit 's blood. They were also produced actively 

 in the chocolate broth produced by the filtration of such rabbit's 

 blood broth as described above. The nature of these poisons is un- 

 certain. The symptoms in the rabbits consist in marked prostration, 



"'Nastjulcoff, Cent. f. Bakt., Ref., xix, 1896. 



27 Cantani, Cent. f. Bakt., xxii, 1897. 



28 Grassberger, Zeit. f. Hyg., xxv, 1897. 



29 Parker, Jour. A. M. A., 72, 1919, 476. 



