groups of streptococci as there are places from which these organisms may 

 be isolated. 



Then Schottmiiller (36) suggested a new classification into strepto- 

 coccus erysipelas, Streptococcus viridans and Streptococcus mucosus, va- 

 rieties recognized by certain distinctive appearances on blood media. 

 While this method was gaining ground in Germany, English bacteriolo- 

 gists were studying the fermentation reactions of streptococci in order to 

 ascertain whether essential differences could be discovered . In this con- 

 nection the researches of Gordon (33) and Andrews and Horder (34) 

 are significant. 



Still another basis for classifying the streptococci has been considered 

 that involving the immunity reactions (35, 37-47). Most investigators 

 think these reactions parallel the blood reactions (43, 44, 45) , while Kligler 

 (35) seems to be at variance with such a conclusion. From his experi- 

 ments he finds a closer relationship between strains fermenting the same 

 carbohydrates than between strains having the same hemolytic power. 



More recently investigations have introduced nothing new so far as 

 fundamental principles of classification are concerned. All of them 

 treat with one, or with a combination of the bases outlined above. Various 

 schemes have been proposed. Most attention has been given to those 

 which make use of the blood reaction. We may mention here the work of 

 Holman (48), Blake (49) and Smith and Brown (45). These authors 

 recognize two main types hemolytic and non-hemolytic, divided into 

 subgroups which depend on the fermentative power of the organisms. 

 And finally, the scheme which has superceded all of these and is now 

 considered as the scheme by some of the most prominent bacteriologists 

 is based primarily on the blood reaction and includes three main groups. 

 Reference is made to the work of Lyall (50), Brown (51) and Park and 

 Williams (52). 



A thorough consideration of the various suggestions has led also us to 

 conclude that the best basis for a preliminary grouping of the strepto- 

 cocci is that last named. The three types recognized are (i) that which 

 hemolyzes the blood corpuscles; (2) that which produces a green colora- 

 tion; (3) that which is indifferent to the presence of blood. 



Detailed technique for differentiating the "blood types": 0.05 cc. 

 culture from seed tube was dropped on the blood agar (0.5 cc. blood 

 plus 9.5 cc. agar) in a petri dish and spread over the entire surface with a 

 special smooth glass rod. The depth of the agar was 2 mm. Precaution 

 was taken to have the blood evenly distributed. The results recorded 

 were obtained from the examination of colonies widely separated after 

 24 hours incubation at 37 C. 



In view of the fact that different laboratories use blood from different 

 animal species we felt it necessary to find out whether the various strains 

 reacted alike on the bloods most commonly used, human, rabbit and 

 sheep. As might have been expected, the response of the organisms to 

 the different kinds of erythrocytes was not the same. The actual ex- 

 perimental findings for 70 cultures are as follows: 



