io 4 SCIENCE REMAKING THE WORLD 



of diseased conditions due to other causes. The rabbit 

 was then chosen for further experiments. 



The results of the first injections of nasal washings 

 from human influenza patients into the lungs of rabbits 

 showed that something in the washings was producing 

 definite and characteristic effects. On the first or 

 second day after injection the rabbits appeared ill, with 

 ruffled fur, inflamed eyes and usually a degree or two of 

 fever. The constant feature of their illness was a 

 sudden drop in certain of the white cells of the blood 

 which fell to half or a quarter of their normal number. 

 These effects were transitory, and after two or three 

 days the animals recovered. If the animals were killed 

 for examination at the height of the attack, their lungs 

 showed evidences of a definite type of injury and dis- 

 organization unlike that found in ordinary pneumonia 

 but similar in many respects to the influenzal damage 

 found in persons dying early in the disease. Usually 

 no ordinary bacteria could be recovered from the in- 

 jured rabbits' lungs and it appeared that the effects pro- 

 duced by the human nasal washings were independent 

 of the presence of commonly recognized microbes. 



By injecting into the lungs a suspension of ground 

 lung tissue from a previously affected rabbit the typical 

 effects just described could be induced successively in 

 a series of animals. In one instance fifteen successive 

 transmissions were obtained before the experiment was 

 discontinued. The persistence of these characteristic 

 results, in spite of the repeated dilution of the original 

 material between transmissions, indicated the presence 

 of a self-perpetuating agent; a living organism or virus. 



