137 



The main results of these investigations into the problem 

 of symbiosis are: (1) the demonstration of different facts con- 

 cerning the technique for the investigation of the phenomenon, 

 and (2) the demonstration of marked individual differences 

 between strains of Pfeiffer's bacilli both with regard to the inten- 

 sity of the , , symbiosis" and in other ways. 



Out of all the strains examined from 1918 to 1921 the following 

 were noted as atypical on the strength of the appearance of the cul- 

 ture: I 25, 33, "34, 55; I 28; P 1, 2, 15; Ms 1, 3, 4, 5, 6, 11, 12, 

 14; H 8, 10, 11. 16, 22, 32, 36, 45, 50, 67, 87, 88, 95, 96, 98, 104, 

 106, 108, 120, 124, 125, 126, 127, 128, 130, 137, 141, 148, 149, 151, 158, 

 161, 171, 173, 176, 178, 179, 181, 185, 193, 199, 200, 201, 205, 208, 207, 

 210, 223, 226, 233, 234, 314a, b, c, d, 318, 319, 322, 324, 330, 332a, b, 

 335, 336; GP 1, 2, 3, 4a, b, 5. 



Growth on Blood Agar. 



The next mark of recognition of Pfeiffer's bacillus we 

 find most frequently in reports on the presence of this bacillus, 

 after haemoglobinophilia and the morphology, is the naked-eye 

 appearance of the growth on blood agar, i. e. agar with the 

 addition of blood in with the corpuscles are not dissolved 

 (or agar smeared with a drop of blood). Quite small, but 

 visible, colourless, „dew-drop" colonies are described as cha- 

 racteristic of Pfeiffer's bacillus. I also, have extensively used 

 blood agar (agar mixed with blood) in the investigation of 

 Pfeiffer's bacillus and in the case of the majority of strains 

 I have found the appearance of the growth on this medium 

 very characteristic. It was soon evident however that the ap- 

 pearance of the cultures of different strains displayed several 

 differences, and that the character of the individual strain 

 usually continued almost unchanged even after numerous sub- 

 cultures. 



The strains which are labelled typical from their growth 

 in the symbiosis test, usually grow in more or less flat, per- 

 fectly clear colonies of a slightly moist appearance, while the 

 atypical most frequently produce small, rounded, colonies with 

 a drier, lustrous appearance. A number of different grades in 

 the appearance of the culture are found and gradual transi- 

 tions between the typical and atypical forms of growth. 



