129 



good haemoglobin (or Fildes) agar, a fact which confirms 

 afresh our assumption about the identical effect of the „V" 

 substance from bacteria and from blood. 



The culture of the atypical strains often has a distinct 

 yellow colour. I have met with a few cultures of Pfeiffer's 

 bacillus which had a rather deep yellow colour (but never so 

 intense as Micrococcus citreus for example). Such strains were 

 called atypical even though the growth was soft and homo- 

 geneous. 



The typical strains always give a good symbiosis reaction, 

 in contrast to the variable intensity of the symbiotic growth 

 among the atypical strains. 



The distribution of typical and atypical strains in healthy 

 persons has already been given and it has also been stated 

 that all the cultures from guinea-pigs were atypical. In in- 

 fluenza and whooping-cough atypical strains were only ex- 

 ceptionally found, in all 5 and 3, respectively, but in measles 

 8 out of 15 were atypical. 



The boundary between typical and atypical growth is not 

 sharp. In the large majority of cases the cultures clearly 

 belonged to the one or other group, but transition forms were 

 sometimes met with. In such doubtful cases the nature of the 

 growth on blood agar and the microscopic picture, will decide. 



On 27. X. 21. a series of symbiosis tests were carried 

 out with the two-fold object of investigating (1) whether the 

 manner of growth of the individual strains kept constant during 

 prolonged cultivation, or whether a given strain could become 

 alternately typical and atypical and (2) whether there was 

 any difference when the inoculation of Pfeiffer's bacillus was 

 abundant or scanty. 



Thirty-three strains were employed, of which 13 (I 1 (a), 5, 6, 

 H 19, 315, 316, 320, 323, 328, 329, " 331, 333, 334) in the original 

 examination (which in the case of the oldest strains was 3 years 

 previously) had proved to be typical, and 20 (Ms 4; H 127, 314b, 

 318, 319, 322, 324, 332b, 335, 336, 419, 420, 423, 424; GP 1, 2, 3, 4a 

 b, 5) were originally labelled atypical. 



In the repeated examination each strain was inoculated in 

 4 parallel streaks, the needle only being filled once, so that 

 the first streak had a liberal amount of the culture and the 



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