SHERWOOD: PLEOMORPHIC STREPTOCOCCI. 253 



lactose. Graham-Smith,^' however, reports numerous strains of 

 \'irulent diphtheria bacilli which produced acid with coagulation 

 of Hiss's serum water medium containing lactose. The diphtheria 

 bacillus grown in dextrose broth gives a tj'pical streptococcus 

 effect, clear broth with fiocculent precipitate settling down. 

 IMacroscopically the colonies on agar are quite similar to normal 

 streptococcus colonies. Its action in neutral red is variable. It 

 must be remembered that one of the strong objections to classifi- 

 cation of any organisms according to fermentation reactions is 

 because of the fluctuating variability that one frequently meets 

 with. I did not think that the pleomoiphic streptococci isolated 

 were identical with B. diphtheria, but I was interested in the ap- 

 parent and suggested relationship between the streptococcus 

 gi'oup and the diphtheria group, as suggested by Gordon and 

 others. I next decided to compare the several strains of pleo- 

 moi'phic streptococci with each other and with B. diphtheria and 

 Streptococcus pyogenes by means of the complement fixation test. 

 I wanted to include a known culture of Streptococcus anginosis, 

 but was unable to obtain it at the time. This work was then con- 

 ducted as follows: 



Antigen. Two kinds of antigen were emploj^ed. In both 

 cases the organisms were grown in plain agar. For one of the 

 antigens suspension of the gi'owth in isotonic salt solution was 

 used. For the other tj^De of antigen the growth was teased off in 

 distilled water and suspension allowed to autolyze and an equal 

 volume of double-strength salt solution added. 



Hemolytic System. Human red blood cells and the corre- 

 sponding hemohtic amboceptor. 



Technique. The technique, barring of course the differences 

 in antigens, was similar to Xoguchi 's modification of the Wasser- 

 mann reaction. As a preliminaiy to this work all of the animals 

 were checked up for normal complement-fixing antibodies with 

 each of the above antigens, and all were negative. 



Following vaccination with the respective strains of organisms, 

 the results showed cross-fixation for all of the strains of the pleo- 

 moiphic streptococci, but no fixation when any of these pleo- 

 moi^phic streptococci were used as antigen with ajiti-Streptococci 

 pyogenes immime sera or B. diphtheria immime sera, nor was the 

 converse true. Neither was there any cross-fLxation between B. 

 diphtheria and Streptococcus pyogenes, although these antigens 

 gave 4 plus reactions with their respective immune sera. In other 



