143 



on the whole, its character relatively unchanged through a 

 long period of cultivation. Some strains always form 1 large 

 colonies, others always small ones; some form colonies regu- 

 larly of a darker colour than others; in some strains the 

 tendency to grow with a rough surface and undulating edge 

 is more developed than in others. 



With regard to the number and distribution of the granu- 

 lations in the colony there is also a certain individuality, 

 but great variations are seen. These granulations are ob- 

 viously rather „labile" formations, in other words their de- 

 velopment is influenced to a large extent by apparently unim- 

 portant „fortui tous" effects. Thus they develop principally 

 round the scratches on the agar surface which are often made 

 in the inoculation (cf. Pringsheim). They are produced chiefly 

 in isolated, well-developed colonies and increase in numbers 

 with increasing age. Sometimes they do not begin to form 

 before the plates have been in the incubator for 2 or 3 days. 



Besides the 10 strains described, 5 others will be seen in the 

 plate, namely the same as — together with I 1 and I 5— are 

 illustrated in the symbiosis test in plate 1. A more detailed description 

 of these 5 colonies, — all from „atypical" strains, — is unnecessary. 

 It need only be mentioned that the unusually dark colony ,,318" was 

 entirely without granulations, while the other 4 had them. The 

 rathe* irregular shape of the surface of „GP 1" was produced in 

 preparing it. 



After this, one might be tempted to think that it would 

 be practically impossible to distinguish Pfeiffer's bacillus from* 

 other bacteria by the appearance of the colonies. But it is 

 not so; the range of shape of colonies of Pfeiffer's bacillus is 

 indeed great but not unlimited. For instance, such dense co- 

 lonies (dark by transmitted, and light by reflected light) as 

 ordinary Staphylococcus colonies, are never met with, nor such 

 large and „waxy" colonies as thpse^of the colon bacillus. In 

 my influenza material I even found that I could regularly 

 diagnose Pfeiffer's bacillus with certainty from the macro- 

 scopic appearance of the colonies on the original plate, but 

 this was far from always possible in the case of Pfeiffer's 

 bacillus obtained from healthy persons. 



The granulations are to a certain extent characteristic of 

 Pfeiffer's bacillus, as in the material used in the investigations 



