216 



3. The appearance of the colonies on a transparent me- 

 dium (Fildes agar) is represented in the various forms of Pfeif- 

 fer's bacillus. 



4. They are Gram negative bacilli resembling morphologi- 

 cally atypical Pfeiffer's bacilli (see plate 3). They do not 

 form spores. 



5. They are decidedly aerobic. 



G. They have the same minimum temperature for growth 

 as the majority of Pfeiffer's bacilli. 



7. They are killed at the same temperature as Pfeiffer's 

 bacillus. 



8. They die out in a couple of weeks in the cold room. 



9. They do not liquefy gelatine or serum. 



10. They do not produce a dark coloration of media con- 

 taining arbutin. 



11. Eight of the strains were vigorous indol-producers. 

 One formed indol in a very slight degree. 



In the following points they were distinct from Pfeif- 

 fer's bacillus: 



1. The good growth on blood agar. This was constant on 

 repeating the test several times. 



2. They showed no symbiosis reaction at all. All the 9 

 strains were tested a short time after they were isolated, on 

 Fildes plates and on agar containing haemolysed blood. In 

 no case did the white air coccus increase the growth. Nor in 

 experiments with 13 other species of cocci and bacilli (each 

 of the 9 strains was tested with 2 of these), nor in a fresh 

 trial in October 1921 with several of the strains and the white 

 air coccus, could any growth-promoting effect whatever be 

 observed. 



3. B. haemoglobinophilus canis however has a marked 

 growth-promoting effect on Pfeiffer's bacillus (see below). 



4. In the previously described experiments where a large 

 number of cultures of Pfeiffer's bacillus were dried for 24 

 hours, the 9 strains of B. haemoglobinophilus canis were also 

 included. While all the Pfeiffer's bacillus cultures were killed 

 this was the case with only one of the strains of the last- 

 named group. 



5. All the 9 strains were capable of marked acid pro- 

 duction in the same haemoglobin glucose broth the reaction 



