• 201 



typical and atypical growth in some cases is difficult to estimate, 

 it might be thought that the indol-positive among the atypical 

 strains should perhaps have been called typical, and the indol- 

 negative among the typical, called atypical. This however is 

 excluded. H314b and d were very markedly atypical, the 

 growth being relatively poor, and very friable, while symbiosis 

 was weak and inconstant. On the other hand most of the 

 indol-negative among the „typical a strains were very decidedly 

 typical both macroscopically and microscopically. 



Atypical strains usually grow worse than „typical". It might 

 therefore be thought that the absence of indol formation in the former 

 was simply due to insufficient growth Rhein, for instance, states 

 that Pfeiffer's bacillus only forms indol when there is a good growth. 



This explanation however, is not probable. Obviously a certain 

 amount of bacteria must be present in order to form a detectable 

 quantity of indol, but in my experience Pfeiffer's bacillus (in liquid 

 media) can produce a very marked indol reaction even when the 

 growth is hardly visible. Of the 4 strains H314a, b, c, and d, which, 

 on solid media, all grew poorly and about the same, indol could be 

 demonstrated in a and c but not in b and d. In carrying out the 

 indol test in the same way as Rhein, I obtained considerably 

 weaker reactions than by the method I usually employed. 



Not only do the typical and atypical growths 

 show a relation to the indol reaction but also to various 

 other phenomena. As previously mentioned the few 

 strains which were particularly resistant to heat, were all 

 atypical. No connection could be shown to exist however, 

 with the minimum temperature for growth. 



Regarding the agglutination of the atypical strains it should 

 be noted the reason they are so scantily represented in the table 

 of agglutination tests is because a large number of the atypical 

 cultures which it was desired to test, either could not be made 

 into homogeneous suspension or were spontaneously agglutina- 

 ted. Of the remainder, several did not react at all with any 

 of the 14 sera, while nearly all the typical strains reacted 

 with one or more of them. Some of the atypical strains 

 however reacted without any definite „spectrum" being predo- 

 minant. A closer investigation of the agglutination relations 

 between different atypical strains would necessitate their being 

 used in the preparation of the sera besides to 14 typical ones, 

 which was not done. 



