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so constant even on cultivation for some years that I have 

 never detected any changes in these factors. (According to 

 Tocunaga, Gosio (3), Wvard, and Cohen & Fitzgerald, a 

 certain, very limited, adaptation can however take place). This 

 power of adaptation is naturally no obstacle to identifying 

 the whooping-cough bacillus by the kind of growth it pro- 

 duces after a few subcultures subsequent to its isolation in 

 pure culture from man. 



On ascitic agar all the whooping-cough bacillus strains 

 grew about as well as on blood agar. The whooping-cough 

 bacillus cannot therefore be regarded as haemoglobinophilic 

 in the true sense. 



Symbiosis tests were made with all the strains on 

 ordinary ascitic agar and on ascitic agar with the addition of 

 haemoglobin, both with the air coccus and a haemolytic 

 Streptococcus. In no case was the growth of the whooping- 

 cough bacillus influenced in the least by the other bacteria. 

 It might be thought that the growth on ascitic agar in pure 

 culture was too good to allow the symbiosis effect to show 

 itself, and also that other species of bacteria might produce it. 

 A medium of ordinary agar containing a few per cent of 

 blood was therefore prepared; the mixture was kept for half 

 an hour at 55° — 60° (which made it rather dark coloured). On 

 inoculation of 79 whooping-cough bacillus strains in streaks 

 on this medium a fairly good growth appeared which however 

 could certainly not be called the maximum 1 . As growth-promo- 

 ting organisms 24 different species of cocci, bacilli and vibrios 

 were used, each of which were tested with 3 or 4 whooping- 

 cough bacillus strains. At a few places a slight inhibition 

 of the growth of the whooping-cough bacillus was observed 

 close to the foreign colonies. In two only of the whooping-cough 

 strains did there seem to be a mild growth-promoting effect, 

 but on repeating the experiment with these two strains with 

 the same „growth-promoting" organism not the slightest effect 

 was observed. 



Among other ways in which the whooping-cough bacillus 

 is constantly different from Pfeiffer's bacillus may be mentioned 

 the greater resistance of the culture against keeping. I 

 have regularly obtained a rich growth by subculturing from 



