207 



bacteria from Pfeiffer's bacillus, but only when a suitable 

 medium is employed. On blood agar with 20 — 25<yo blood it 

 may sometimes happen that the growth is too feeble and the 

 amount of blood corpuscles to be dissolved, too large to give 

 distinct transparency. By employing ordinary Fildes agar with 

 the addition of 5 or 10o/o blood the haemolysis was always 

 extremely marked. Only one strain failed to give marked 

 haemolysis before the lapse of a couple of days and the clear 

 margin remained narrow. In all the other cases there was 

 complete haemolysis after 24 hours. In agreement with the 

 American authors I found this haemolysis closely resembles 

 that around colonies of the true haemolytic Streptococci. The 

 blood agar beneath the culture and in a narrow, outwardly 

 fairly sharply defined border around it, is completely transpa- 

 rent and partially decolorised. 



Haemolysis is moreover a constant character. It has 

 already been mentioned on p. 139 that a large number 

 of haemoglobinophilic non-haemolytic bacilli (that is to say 

 Pfeiffer's bacilli) had in no case acquired the power 

 of haemolysing after many subcultivations, which could be 

 demonstrated on ordinary blood agar. In October 1921 ino- 

 culations were made on the recently mentioned improved blood 

 medium, of about 70 strains of Pfeiffer's bacillus, the oldest 

 of which had been cultivated for more than 3 years, together 

 with 7 strains of haemoglobinophilic bacteria which had been 

 isolated about a year earlier and were then haemolytic. In 

 the new investigation none of the Pfeiffer's bacilli showed hae- 

 molysis, while the originally haemolytic strains had all pre- 

 served this property. All the haemolytic strains from the 

 inoculations on 17. IX. were kept until 1. XL, when they were 

 again examined for haemolysis. The result was exactly the 

 same as in the first investigation. Both times one of the strains 

 (the one referred to above) gave slow and comparatively weak 

 haemolysis, while all the others even after 24 hours' growth 

 showed very marked haemolysis. 



With regard to „symbiosis" my haemolytic strains behaved 

 very differently. In some this character was entirely lacking, 

 but in the majority it was present to a marked degree. 



The macroscopic appearence of the cultures was as a rule 

 „alypical"; in some cases the consistence was friable, more 



