Immunity 517 



The organism is aerobic and scarcely grows at all where the 

 supply of oxygen is not free. 



In bouillon a scant development occurs, small whitish 

 particles appearing upon the surface, subsequently sinking 

 to the bottom and causing a "wooly" deposit there. The 

 bacillus grows more luxuriantly upon culture-media contain- 

 ing hemoglobin or blood, and can be transferred from culture 

 to culture many times before losing vitality. 



Vital Resistance. Its resisting powers are very re- 

 stricted, as it speedily succumbs to drying, and is certainly 

 killed by an exposure to a temperature of 60 C. for five 

 minutes. It will not grow at any temperature below 28 C. 



Specificity. From the fact that the bacillus is found 

 chiefly in cases of influenza, that it is present as long as the 

 purulent secretions of the disease last, and then disappears, 

 and that Pfeiffer was able to demonstrate its presence in all 

 cases of uncomplicated influenza, it seems that his conclu- 

 sion that the bacillus is specific is justifiable. It is also 

 found in the secondary morbid processes following influenza, 

 such as pneumonia, endocarditis, middle-ear disease, menin- 

 gitis, etc. Horder* has cultivated it from the valvular vege- 

 tation of 2 cases of endocarditis following influenza. 



Davis f found the influenza bacillus in the respiratory 

 passage of a large number of patients suffering from whoop- 

 ing-cough. 



Pathogenesis. The bacillus is pathogenic for very few 

 of the laboratory animals, the guinea-pig being susceptible 

 of fatal infection. The dose required to cause death of a 

 guinea-pig varies considerably. 



Pfeiffer and BeckJ produced what may have been influenza 

 in monkeys by rubbing their nasal mucous membranes with 

 pure cultures. 



Immunity. As influenza is a disease that commonly re- 

 lapses, and from which one rarely seems to acquire protection 

 against future attacks, there must be scarcely any immunity 

 induced through ordinary infection. Moreover, the organism 

 once finding its way into the body seems to remain almost in- 

 definitely, especially when, as in pulmonary tuberculosis, 

 there is already present an abnormal condition furnishing 

 discharges or exudates in which it can thrive. 



* "Path. Soc. of London," "Brit. Med. Jour.," April 22, 1905. 

 t "Jour. Infectious Diseases," in, 1906, i. 

 J" Deutsche med. Wochenschrift," 1893, xxi. 



