488 PATHOGENIC MICROORGANISMS 



had had influenza, came down after two or three days. Finally, pure 

 cultures of Pfeiffer, and mixed cultures of Pfeiffer bacilli with pneu- 

 mococci, staphylococci and streptococci were injected into the noses 

 and throats of 14 healthy people who had not had influenza. No 

 symptoms followed these injections. More recently, Olitsky and 

 Gates 10 reported upon experiments they had made in the 18 months 

 previous to publication, beginning during the epidemic wave of 1918. 

 They intratracheally inoculated secretions from influenza patients in 

 the early stages, into rabbits. After a short period these rabbits 

 developed fever, leucopenia, minute pulmonary hemorrhage, and 

 pulmonary edema and emphysema. The rabbits did not ordinarily 

 die of the disease, but when they killed them in the active stages and 

 filtered the material from these pulmonary lesions, they were able to 

 continue producing such disease in rabbits with the filtrate. They 

 proved by careful experimentation that the symptoms and lesions they 

 obtained were not due to bacteria in the ordinary sense of the word. 

 It is impossible at the present time to comment conclusively on these 

 results, but the evidence is submitted to show that there is a consider- 

 able amount of evidence at the present time which should make one 

 conservative in definitely claiming etiological relationship for the 

 influenza bacillus. 



EPIDEMIOLOGY OF INFLUENZA 



As stated before, the etiological and diagnostic difficulties in con- 

 nection with influenza are such that records of the disease are less 

 apt to be reliable than would be similar records of smallpox, diph- 

 theria, etc. However, a great deal is known about past epidemics 

 which have been described with sufficient accuracy to permit us to 

 recognize them definitely as true influenza epidemics. A great deal 

 has been written in the past and is available in the works of Caienus 

 of Grief swald (1579), Jacques Pons of Lyon (1596), Sydenham 

 (1675), Slevogt (Jean, 1712), Haygrath and Hamilton (1775), 

 Pringle and 1 Huxham, Massin (Strassburg, 1858) and many others. 

 Leichtenstern, who has written a vary thorough treatise on influenza 

 tabulates the great influenza epidemics of the world as follows: 



Less extensive outbreaks seem to have prevailed in different parts 

 of the world between 1709 and 1912. 



Olitsky and Gates, Jour. Exper. Med., 33, 1921, No. 2 and 3. 



