CLONAL PHENOMENA 



Streptomycin or to lysis by a particular bacteriophage. 

 Further work was subsequently published in collaboration 

 with Stone (1945). The experimental basis for the inter- 

 pretation was our ability to maintain virus in the quality 

 for thirty passages in the amniotic cavity in the sense that it 

 still showed the typical F/G ratio and failed to produce 

 haemagglutinin in the allantoic cavity. This was done — not 

 without much labour — by limit-dilution passage in the 

 amniotic cavity with transfer of selected fluids of low FjG 

 ratio. In general, a full titration in the amniotic cavity and in 

 the allantoic gave results of the type shown in Table I. This is 

 taken from a later investigationof another strain of influenza A, 



Table i . Titration of an influenza A fluid obtained from an 

 inoculation of an -type fluid at limiting-infective dilution 



Amniotic Allantoic 



Evidence of infection was the occurrence of haemagglutination in 

 amniotic or allantoic fluid according to the route of invaluation. Phase 

 or D determined on the results of haemagglutinin titrations with both 

 fowl and guinea-pig cells. 



If we took one of the 0-type fluids obtained at limit or 

 near-limit dilution and titrated this by the same method, we 

 obtained a similar pattern of results, and, as has already been 

 stated, 0-phase virus could be maintained indefinitely by 

 this method. 



The essence of the experiments was the demonstration that 

 by using a method based on just the same principles as are 



18 



