139 



where the growth is thicker the spreading will take place to 

 a considerably greater extent and the same applies to media 

 containing dissolved haemoglobin. This „surface" growth in 

 its milder degrees is merely characterised by the edge of the 

 culture not being clear-cut but shelvy. In the more intense 

 surface growths flat tongues project from the inoculated area 

 which together form an undulating border of as much as 3 —4 

 mm. in breadth. 



The various points enumerated were (Jan. 1920) carefully 

 investigated in the case of the strains given on p. 108. It would 

 be idle to attempt to describe the variegated, finely graded 

 pictures which were seen. The most marked feature which 

 arose out of the experiment was that a few strains were in- 

 clined to grow with fringes to quite a large extent, namely 

 I 1, and P 23. Of strains acquired later I 33 had the same 

 peculiarity. These 3 strains, but particularly the first, have 

 shown this characteristic on different media and after cul- 

 tivation for a prolonged period, to a greater de<gree than any 

 of the other strains kept going for a long time. 



Pfeiffer's bacillus, — according to definition — gives no 

 haemolysis on blood agar. This negative property has proved 

 to be constant, since the hundred or so stock strains in Sept. 

 1920, did not give haemolysis in a single instance when ino- 

 culated on blood agar.' The cultures were observed during 

 a week in the incubator. 



Appearance of the Colonies. 



In cultures produced by liberal inoculation, Pfeiffer's ba- 

 cillus displays its most characteristic and individualised macro- 

 scopic appearance on blood agar and in the symbiosis test 

 on weakly haemoglobin-containing agar, while the growth 

 is less characteristic on agar containing dissolved haemoglobin 

 (in natural or transformed condition) in large quantity. But 

 when it is a question of examining isolated colonies, the latter 

 is the medium which gives the most characteristic pictures of 

 Pfeiffer's bacillus in general and presents the most variable 

 individual characters of the various strains. 



