DIPHTHEROID ORGANISMS 33 



forms are so slight, bacteriologically speaking, such a method suggested 

 possibilities for more definite classification. 



The strains studied were obtained from the Museum of Natural History and 

 were marked as follows : C. hoagii, C. flavidus (Mellon), C. pseudodiphtheriae, 

 C. xerosis, C. enzymicus (Mellon), and C. flavidus (Morse). 



Agglutinating serums were prepared in rabbits by giving intravenous injec- 

 tions of fresh agar cultures heated at 56 C. for 30 minutes. Increasing doses 

 were given every week until a whole culture was reached. The animals gained 

 weight throughout treatment and were bled 10 days after the last injection. 

 Preliminary titrations were made with each of the serums against homologous 

 and heterologous strains, and double absorption of each serum was made with 

 organisms which evidenced some affinity for the agglutinins present. 



The results of the absorption experiments indicate that C. hoagii is 

 more inclusive in its antigenic elements, since it possesses group agglu- 

 tinins for all the other strains, excepting C. xerosis. C. flavidus (Mel- 



TABLE 2 

 COMPARATIVE RESULTS 



Flavidus (Morse) Flavidus (Mellon) 



Dextrose 3.3 cc 2.0 c c 



Maltose 2.0 1.7 



Saccharose 2.5 1.4 



Glycerol 3.3 2.6 



The figures represent the amount of N/20 NaOH required to neutralize 5 c c of broth 

 culture incubated 1 day at 37 C. Growth was heavy in both sets. The Mellon strain gave 

 a flocculate growth and the Morse culture was uniformly clouded. 



Ion) has no group agglutinins for any of the others and appears to be 

 highly specific. The results vary somewhat as compared with Morse's 

 complement fixation results. Mellon's flavidus shows no group agglu- 

 tinins at all, although Morse obtained partial cross fixation with her 

 strain. It appeared likely that the former culture sent to the Museum 

 of Natural History as a "B. flavidus," isolated by Mellon, was not a 

 flavidus type. When its homologous serum was absorbed with C. 

 "flavidus" (Morse), the specific agglutinins remained unchanged. That 

 complete absorption by the heterologous strain took place is evident 

 from the table. Macroscopically, the Morse culture differs markedly 

 on plain agar from the Mellon strain. The latter develops a dull, dry 

 growth, with a tendency to flocculate readily in NaCl solution, whereas 

 the former is moist and glistening in its growth. In carbohydrates the 

 comparative results were as shown in Table 2. 



The relative rate of acid-production by both strains is obviously 

 different. Prolonged cultivation may give somewhat different results, 

 but it has been shown by several workers that the maximum acid- 



