DIPHTHEROID ORGANISMS 41 



it into a bacillus. In the serologic experiments described subsequently it is 

 shown that the coccus is antigenically distinct from the bacillary type and that 

 the extremely short types which are identical in appearance with cocci are 

 merely altered bacillary forms. These "cocci," to be designated here as 

 Strain 28, are antigenically the same as the long, granular rods. 



Diphtheroid cocci were grown on Loeffler's serum for 27 generations, and no 

 change was noted in morphology. The organisms remained cocci. On glucose 

 serum medium the forms developed considerably larger and thicker, but were 

 typical diplococci in outline. On agar of various H-ion concentrations ranging 

 from 6.1-5.2, no change in form was observed. The use of potassium bichro- 

 mate in broth containing various amounts of acid failed to alter the coccus. 



A bacillary strain of C. enzymicus was cultivated on plain agar at 28 C. for 

 several days and subcultures made from day to day. After one week at this tem- 

 perature, stained specimens from different slants showed forms which could 

 hardly be distinguished from diplococci. These proved on close examination 

 to be minute rods unevenly stained and bipolars. Such cultures, if transferred 

 to serum medium, assumed the typical bacillary form. Figure 18 illustrates 

 clearly how readily one may err in calling these forms cocci. By comparing 

 them with the true cocci shown in Figure 16 the difference can be seen. 



Behavior of Coccus and Bacillary Types in Carbohydrates. Sugar broths 

 (1.0+ to phenolphthalein) were made in the usual manner, and duplicate sets 



of tubes were inoculated from a 24-hour old agar culture of C. enzymicus 

 (coccus) and C. enzymicus (bacillary). After 8 days' incubation at 37 C. the 

 titrable acid formed in each of the carbohydrates was determined by addition 

 of N/20 NaOH, using phenolphthalein as an indicator. Titrations were done 

 in the cold. Five c.c. of broth were used in a total volume of 50 c.c. with 

 distilled H 2 O. 



Examination of the tubes after inoculation with both strains showed the 

 marked difference in rate of growth of the organisms. After 8 hours the coccus 

 type had clouded all of the sugar broths heavily. The bacillary type developed 

 more slowly, and the intensity of clouding after 24 hours approximated that 

 produced by the coccus in a third of the time. Both series showed fine granu- 

 lation and sedimentation, but this was more pronounced in the case of the 

 coccus. 



The acid-production is given in Table 1. The figures represent the amount 

 of N/20 NaOH required to neutralize acid. 



The tabulation shows at a glance that, with the exception of glycerol and 

 dextrin, perhaps, both types behaved similarly in the carbohydrates used. This 

 might be an argument for similarity or relationship of both organisms. The 

 difference observed in glycerol, however, was too marked to escape notice and 



