THE INFLUENZA BACILLUS 323 



Detection of the Influenza Bacillus in Sputum. The direct microscopic 

 examination of stained smears of sputum may give considerable infor- 

 mation as to the probable presence of influenza-like bacilli. The 

 frequent presence of other influenza-like bacilli in the throat secretions 

 leads to so much doubt that it is advisable from the start to make use 

 of plate cultures, the best medium being nutrient agar freshly smeared 

 with a film of rabbit's blood. 



Pathogenesis. The bacillus of influenza, in so far as experiments 

 show, produces a disease at all similar to influenza only in monkeys 

 and to a less extent in rabbits. When a small quantity of culture on 

 blood agar, twenty-four hours old, suspended in* 1 c.c. of bouillon, was 

 injected intravenously into rabbits, Pfeiffer found that a characteristic 

 pathogenic effect was produced. The first symptoms were developed 

 in one and a half to two hours after the injection. The animals became 

 extremely feeble, lying flat upon the floor, with their limbs extended, 

 and suffered from extreme dyspnoea. The temperature rose to 41 C. 

 or above. At the end of five or six hours they were able to sit up on 

 their haunches again, and in twenty-four hours had recovered. Larger 

 doses caused the death of the animals inoculated. These results are 

 attributed by Pfeiffer to toxic products present in the cultures, and in 

 none of his experiments was he ever able to obtain effects resembling 

 septicremic infection. In some of the experiments on monkeys, these 

 animals, when cultures were rubbed into the nasal mucous membrane, 

 showed a febrile condition, lasting for a few days; but in no instance 

 has Pfeiffer observed a multiplication of the bacilli introduced. 



The cell bodies of the bacilli seem to possess considerable pyogenic 

 action. 



Immunity. Possibly an immunity for a short period against the 

 influenza poison may be established after an attack. At least in three 

 experiments made by Pfeiffer on monkeys, these animals, after recover- 

 ing from an inoculation with bacilli, seemed to be much less susceptible 

 to a second injection. 



Distribution of Influenza Bacilli in the Body. In patients suffering 

 from influenza the bacilli are found chiefly in the nasal and bronchial 

 secretions. In acute uncomplicated cases they may be observed micro- 

 scopically in large masses, and often in absolutely pure culture; the 

 green, purulent sputum derived from the bronchial tubes is especially 

 suitable for examination. The older the process is, the fewer free bacilli 

 will be found and the more frequently will they be seen lying within 

 the pus cells, instead of being embedded free in the secretion as at first. 

 At the same time they stain less readily and present more irregular 

 and swollen forms. Very frequently the influenza process invades 

 portions of the lung tissue. In severe cases a form of pneumonia is 

 the result, which is lobular and purulent in character, and accompanied 

 by symptoms which may be somewhat characteristic for influenza, or, 

 again, almost identical with bronchopneumonia due to the pneumo- 

 coccus. The walls of the bronchioles and alveolar septa become drnx-ly 

 infiltrated with leukocytes, and the spaces of the bronchial tubes and 



