C. DOBBLL 333 



In a preliminary note Thaysen (1911) announces that he has iso- 

 lated and studied eight different races of coli-typhosus-gvon^ organisms. 

 These have the following properties : Four races ferment dextrose, 

 maltose and lactose, but not saccharose. By cultivation, however, thej^ 

 acquire the power of splitting this sugar also. One race splits dextrose 

 and maltose, but not saccharose or lactose. But it can acquire the 

 power of splitting the last named sugar. It appears to be identical 

 with B. coli niutahileK Two races are similar to the preceding, but 

 can acquire the power of splitting saccharose. They appear to be 

 similar to B. imperfectum" of Burri. Finally, one race splits dextrose, 

 maltose, and saccharose, but not lactose. It can, however, acquire the 

 power of fermenting this substance '. 



Up to this point I have mentioned only those results which are 

 essentially similar to Massini's. I have purposely avoided referring 

 to the work of Burri and his collaborators. The work so far is at 

 the same stage, but Burri's work represents a step forward. Let us 

 now consider it. 



The papers of Burri and Diiggeli (1909) and Burri and Andrejew 

 (1910) may be considered — for the present purposes — as parts of the 

 admirable work of Burri (1910), which I shall now endeavour to 

 chronicle. 



Burri has isolated^ a race of organisms of the coli-typhosus group 

 which are unable to ferment saccharose and lactose. He calls this 

 race Bacterium imperfectmn. It never acquired the power of splitting 

 lactose : but on the other hand, when grown in media containing sac- 

 charose, some colonies acquired the power of splitting this sugar. The 

 saccharose-splitting mutant Burri names B. perfectum^. (Both organisms 

 belong to the paratyphosus sub-division oi coli-typhosus organisms.) 



Burri's observations were originally made upon organisms grown in 

 " shake-cultures'' " — not on Endo's medium. The cultures were made 



1 The lactose-splitting mutant from B. coli mutabile is, according to Thaysen, unable 

 to produce Indol. It is therefore not a typical B. coli. 



- Vide infra. 



'■' Thaysen's full paper has appeared whilst this article is in the press. See C, B. 

 Bait. I. Abt. (Orig.), Vol. lxvii. 1912, p. 1. 



* From fermenting grass. 



'" On analogy with this, he proposes to call the lactose-fermenting mutant derived by 

 Massini from the non-lactose-fermenting B. coli mutabile by the name B. coli mutatum. 



^ lu a shake-culture the organisms are distributed, by shaking, through a liquefied 

 jeUy — in this case containing saccharose. When the jelly has set, the isolated organisms 

 produce colonies. Those which ferment the sugar produce bubbles of gas in the jelly and 

 can tlierefore be readily distinguished. 



