EPIDEMIC INFLUENZA 495 



inflammation results followed generally by recovery. 

 Many strains in liquid culture produce, however, a marked 

 peritonitis, and Blake and Cecil, by means of liquid cul- 

 tures passed through a series of mice and subsequently 

 of monkeys and then applied to the riaso-pharynx of 

 monkeys, induced fever and croyza, and inoculated intra- 

 tracheally produced bronchitis and broncho-pneumonia 

 with extensive haemorrhages. 



The toxicity of liquid cultures appears to be due to 

 the formation of a certain amount of an extra-cellular 

 toxin. 



^Etiology of epidemic influenza. With the discovery of 

 the B. influenzce in the epidemic of the 'nineties, the 

 causal relationship of the organism to the disease was 

 considered to be established until the epidemic of 1918-19. 

 A number of workers then announced that they had been 

 unable to find the B. influenzce in a considerable propor- 

 tion of typical cases, while ha3molytic streptococci, 

 pneumococci and Gram-negative cocci were fairly con- 

 stantly found, particularly in the severe pneumonia 

 which characterised the later stages of this epidemic. 

 Doubt now began to be cast upon the causal relationship 

 of B. influenzce to epidemic influenza, and some observers 

 attempted to show that the disease is due to an invisible 

 virus, e.g. Nicolle and Lebailly 1 ; Bradford, Bashford 

 and Wilson 2 ; Gibson, Bowman and Connor. 3 The 

 work done in this direction is, however, quite inconclusive, 

 and some of it is not free from error. 



What renders the matter more perplexing is the diffi- 

 culty of transmitting the disease experimentally to man. 

 Rosen au, for instance, sprayed the noses and throats 

 of ten volunteers with the mixed nasal and throat washings 



1 Ann. de Vlnst. Pasteur, xxxiii, 1919, p. 395. 



2 Quart. Journ. Med., 1919, xii, p. 259. 



3 Spec. Rep. Series, No. 36, Med. Research Committee. 



