217 



of which none of the strains of Pfeiffer's bacillus were able 

 to change to any appreciable extent. 



Agglutination experiments were not done as the cultures 

 (on Fii.des agar) could not be made into a homogeneous 

 suspension. 



From this summary it is clear that the bacilli from 1 the 

 prepuce of dogs are closely related to Pfeiffer's bacillus but 

 however differ from it in important points. 



Davis (6) has called attention to the fact that while almost 

 all species of bacteria promote the growth of Pfeiffer's ba- 

 cillus, it forms an exception itself. A growth of Pfeiffer's ba- 

 cillus is helped neither by the same strain nor by any other 

 strain of Pfeiffer's bacillus. 



I was able to fully confirm this. Agar was used with the 

 addition of so much dissolved haemoglobin that the bacillus 

 grew in pure culture rather better than on blood agar but 

 that the growth fell sufficiently short of the maximum for 

 it to be considerably increased by the air coccus. A typical 

 indol-posilive Pfeiffer's bacillus was inoculated in the usual 

 manner in parallel straks, and between was inoculated another 

 Pfeiffer's bacillus, not however at points but covering a rather 

 larger area. The test was carried out with the homologous 

 strain, with typical indol-negative strains, and with various 

 atypical strains among which were all the 6 from guinea-pigs. 

 In no case was the slightest growth-promoting effect observed. 



19 strains of haemolytic, haemoglobinophilic bacteria were 

 also entirely inactive in this respect, as regards Pfeiffer's ba- 

 cillus. But in the case of whooping-cough bacilli an undoubted 

 though rather weak growth-promoting power was observed. 



All the 9 strains of B. ' haemoglobinophilus canis were 

 examined for growth-promoting effect which proved to be 

 present in all the cases to a very marked degree. 



The results of these tests indicate that the haemolytic, 

 haemoglobinophilic bacteria may be looked upon as more closely 

 related to Pfeiffer's bacillus than the two last species. This 

 is in conformity with the other properties of these species 

 of bacteria. 



