EPIDEMIC INFLUENZA 103 



signs of the human infection, the typical changes in the 

 blood might be used as an indication of successful trans- 

 mission and it appeared probable that some local injury 

 might be found in the lungs of the animals which would 

 account for the characteristic defect in the resistance of 

 the lungs following human influenza. 



Influenza is transmitted from person to person by the 

 secretions of the respiratory tract, so the first experi- 

 ments were undertaken with washings from the noses 

 and throats of human patients in the early hours of the 

 disease. These washings of course contained many 

 varieties of bacteria, but it was expected that in favour- 

 able instances the ordinary bacteria of the nose and 

 throat would be suppressed through the natural resis- 

 tance of the animal and that the specific effects of an 

 extraordinary microbe might thereby be revealed. 



In a short series of experiments monkeys were found 

 to be unsuitable for use in the study of influenza both 

 because of their scarcity and because of the frequent 

 presence of pulmonary tuberculosis in the available 

 monkeys. These preliminary experiments, however, 

 gave a clue to a method of injecting the nasal washings 

 which promised definite results. Injections of the 

 washings into the nose and throat, the eyes, the blood, 

 and under the skin produced no distinctive effects. 

 But when the injections were made into the trachea, 

 so that the material ran down into the lungs, the mon- 

 keys showed a decrease in the white cells of the blood, 

 such as is characteristic of human influenza. This 

 suggestive sign could not be correlated with local dam- 

 age to the lungs, however, because of the frequency 



