324 BACTERIOLOGY. 



their vitality for from a few days to two or three 

 weeks. 



Pathogenesis. The bacillus of influenza, in so far as 

 experiments show, produces the disease only in monkeys 

 and to a less extent in rabbits. From numerous ex- 

 periments made by Pfeiffer on guinea-pigs, rats, mice, 

 and pigeons these animals seem to be more or less in- 

 susceptible to influenza. When a small quantity of 

 culture on blood-agar, twenty-four hours old, sus- 

 pended in 1 c.c. of bouillon, was injected intrave- 

 nously 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 septicsemic 

 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, and in one case an abscess was produced 

 from an injection into the subcutaneous intercellular 

 tissues: but in no instance has Pfeiffer observed a mul- 

 tiplication of the bacilli introduced. Recently Cantani 

 has shown that it is possible to produce an infection of 

 influenza in rabbits when inoculated with small doses 

 ( to J c.c.) of living bacilli, provided the point of least 



