1912.] 



On the Variability of Streptococci. 



401 



reactions in these media of a series of selected strains of streptococci varied 

 independently from time to time under the conditions of ordinary laboratory 

 cultivation, and could in certain cases be made to vary very greatly by 

 growing the organisms for longer or shorter periods in media containing 

 particular " sugars." 



The conclusions which were drawn from these and similar observations 

 have been strongly controverted by Gordon (1911, 4), who issued an article 

 containing a series of criticisms of my results, and reasserted his claim to 

 have differentiated distinct types of streptococci by means of his tests. The 

 grounds on which he based this contention, unfortunately, appear to involve 

 some slight misapprehension of the question under discussion. This was 

 whether the ''types" thus differentiated are fixed and independent, or 

 merely temporary and liable to variation and interchange of characters. 



On the other hand, the later work of Beattie and Yates (1911, 5) com- 

 pletely confirmed the views which I had put forward, since they found it 

 impossible to differentiate between the various strains of streptococci which 

 they used, and state that in their hands " Gordon's tests have proved quite 

 unreliable for this purpose." 



For the purpose of throwing further light upon the subject, I have 

 examined the behaviour of a single streptococcus freshly isolated from the 

 human subject in regard to Gordon's tests, both after growth in certain 

 ordinary culture media, and after a series of successive passages through 

 the mouse. I have also incidentally re-examined the reactions of some of 

 the streptococci employed in my previous experiments after the lapse of a 

 further period of 18 months. The results obtained are in entire agreement 

 with my former conclusions. 



Methods. 



The methods and precautions used were the same as those employed in 

 my previous work (1911, 3). But, in view of certain doubts expressed by 

 Gordon, it may be well to state that throughout the whole of my investi- 

 gation of the fermentation tests the " sugars " used in the preparation of 

 the media have been pure substances obtained from Merck. Further, in 

 every case where the reaction appeared to give a negative result, the strepto- 

 cocci in the tube in question were proved by successful sub-culture to be 

 actually living before the result was accepted as negative. 



The streptococcus A was isolated post mortem, from the blood of a case of 

 ulcerative endocarditis, and appeared to be present in pure culture. It 

 was three times plated out, and propagated on each occasion from a single 

 isolated colony. Its reactions were then tested in Gordon's media. 



A stock culture was established in stab agar, and propagated in sub-culture 



