251 



The following characters were common to the large ma- 

 jority of strains. 



(r). Increase of growth around colonies of other species of 

 bacteria. In a few strains this character was absent or very 

 poorly developed. 



(s). Death after half an hour's heating at about 50°. A 

 few strains however resisted a slightly higher temperature. 



Since all the strains cultivated, so far as was investigated, 

 possess such a large number of common characters, they ought, as 

 has hitherto been the case, to be classed as the same species. 

 This receives additional support from the following marked 

 differences between these bacilli and closely related species. 



12. The haemo lytic haemoglobin ophilic ba- 

 cilli differ from Pfeiffer's bacilli (a) in the presence of hae- 

 molysis, (b) in only occurring as saprophytes, (c) in a less 

 strict dependence on haemoglobin and usually also, (d) in a 

 coarser morphology and (e) in a slighter resistance to keeping. 



13. Bac. haemoglobinophilus canis differs from 

 Pfeiffer's bacillus (a) in its richer growth on blood agar, (b) 

 in its growth not being increased by other bacteria, (c) in 

 promoting the growth of Pfeiffer's bacillus, (d) in its greater 

 resistance to drying, (e) in having well developed fermentative 

 powers. 



Otherwise these two species resemble Pfeiffer's bacillus 

 in so many points that they are naturally regarded as closely 

 related forms. 



14. Bordet's whooping-cough bacillus is considered to be 

 more divergent. The aim here has been to show how con- 

 stant and easily demonstrable the series characters is which 

 distinguishes it from Pfeiffer's bacillus. These characters are: 



(a). The appearance of the culture on blood agar. 



(b). Haemolysis of a definite kind on this medium. 



(c). The slow growth. 



(d). Growth on blood-free ascitic agar. 



(e). No growth or slight growth on the media which are 

 particularly suitable for Pfeiffer's bacillus. 



(f). The growth is not promoted by other bacteria. 



(g). It has itself a growth-promoting action on Pfeiffer's 

 bacillus. 



(h). The greater resistance against keeping. 



