DIPHTHEROID ORGANISMS 43 



mixture of bacteria and serum was incubated at 37 C. for I 1 /* hours, kept at 

 4 C. over night, and then centrifugated for 20 minutes at high speed. The 

 supernatant serum, pipetted off, was added to another heavy sediment of 

 organisms, obtained as in the preceding, and the absorption repeated, after 

 which agglutination tests were made. A series of dilutions were prepared 

 with each original serum and tubes set up at the same time as the absorbed 

 serum. 



The results of these absorption experiments are decisive. A serum 

 prepared with the coccus possesses no agglutinins for the bacillary 

 diphtheroid and when absorbed completely with this bacillary strain 

 evidences no reduction in its agglutination titer against the homologous 

 coccus. The coccus serum when absorbed with a bacillary strain altered 

 morphologically by cultivation at 28 C. for 10 days so that the organism 



TABLE 3 

 ABSORPTION EXPERIMENTS WITH BACILLARY SERUM 



Serum C. Enzymicus Bacillary 



1-10 1-20 1-50 1-100 1-200 1-400 1-800 1-1600 1-2000 1-3000 



0. enzymicus (bacillary) ++ ++ ++ + 



C. enzymicus (coccus) + 



After absorption with C. enzymicus (coccus) 

 C. enzymicus (bacillary) ++ ++ ++ ++ + 



After absorption with C. enzymicus Strain 28 

 C. enzymicus (bacillary) ++ + 



could not be distinguished from cocci, lost none of its agglutinating 

 power for the coccus. Again evidence is adduced that the change on 

 the part of the bacillus was merely an appearance, and that the organ- 

 isms were not true cocci, but extremely short bacilli, altered perhaps by 

 changes in surface tension to assume a form remarkably like cocci. 

 Antigenically these organisms are therefore distinct from the coccus 

 type. In Table 3 they are shown to be identical with the original bacil- 

 lary form. The conclusion to be drawn from this experiment is that 

 the coccus has no antigenic elements in common with the bacillus. 



The next experiment, made with a serum produced with the bacil- 

 lary strain of C. enzymicus, gave additional evidence in another direc- 

 tion and confirmed the difference of the two organisms. The serum, 

 although agglutinating its homologous culture as high as 1-2000, gave 

 agglutination in 1-10 for the coccus. This in itself would be an argu- 

 ment against antigenic relationship. The fact that a bacillary strain is 

 never free from cocci, however, would readily explain slight agglutina- 

 tion which might occur. This interesting point is shown quite clearly 



