87 



Distribution in Cases of Influenza. 



Both the series are unfortunately very small, so that con- 

 elusions are difficult to draw. It will be observed, however that, 

 while in the 1918 epidemic a high proportion of the strains contained 

 the group antigens, in the 1922 epidemic the proportion was 

 lower, being about the same as in the strains isolated from 

 pneumonia during the inter-epidemic period; i.e., there is no 

 evidence of a special pathogenic type. 



The Question of Epidemic Types. 



Do epidemic types occur ? In this connection certain 

 observations, though not conclusive, are perhaps worth recording. 

 The strains SI and S4 (vide Table 4), as well as two other strains 

 S2 and S3 with which I have not prepared sera, all came from cases 

 of influenzal pneumonia during an outbreak of influenza in 

 Sheffield in May 1920. As has been remarked, these S strains, 

 though exhibiting, at least in the case of Si, some slight relation- 

 ship with the other sfciains used as standards, were conspicuously 

 " individual " ; their predominant antigen did not occur among 

 the other strains nor has it appeared among the strains isolated 

 in the London area from ordinary non-influenzal pneumonias 

 during the inter-epidemic period 1920 to 1921. 



In April 1921, however, Dr. Nixon of Bristol sent me a 

 specimen of lung from an infant of 1 year who died of catarrhal 

 pneumonia : the consolidation was typically lobular. An 

 abundant growth of influenza bacilli was obtained which agglu- 

 tinated strongly with SI serum and absorbed the agglutinin 

 of this serum completely (a few pneumococci of the " atypical " 

 group were also found). There was no epidemic prevalence 

 of influenza in Bristol at the time, but ten days later a specimen of 

 sputum was received from Bristol from a case described by 

 Dr. Nixon as typical " violet " influenzal pneumonia with great 

 prostration. This again yielded an abundant growth of in- 

 fluenza bacilli (but no pneumococci) agglutinating strongly with 

 Si serum and absorbing a high proportion of its agglutinin. 

 No connection could be established between these cases, and no 

 further specimen from influenzal pneumonia was received from 

 Bristol till July 1921, when again sputum from a case of " violet " 

 pneumonia yielded an abundant culture of influenza bacilli 

 agglutinating with Si serum and with a serum prepared with the 

 strain from the second Bristol case. At the same time, however, 

 a similar strain was isolated from a case of ordinary lobar 

 pneumonia in Birmingham, indicating at once that the SI antigen 

 was not confined to strains from influenzal pneumonia. Further- 

 more, during the epidemic of January, 1922, the Si antigen has 

 appeared in strains from two healthy school children and from 

 one case of ordinary lobar pneumonia in London, while among 

 the strains from cases of influenzal pneumonia during this London 



