BACTERIUM VIOLACEUM. 279 



favorable cases the pellicle may assume a pale violet 

 color. 



Milk. — In some cases it is coagulated, but it usually re- 

 mains fluid and is violet in color, at least forms a violet 

 cream layer. 



Chemical Activities. — In grape-sugar bouillon there 

 is formed little acid and no gas. It produces abundant 

 HjS and a moderate amount of indol. 



Regarding the pigment (janthin), see page 67. 



From the one just described Ave are unable to dis- 

 tinguish, by any peculiarities worth mentioning, the 

 Bacterium janthinum Zopf (Sweden and America), 

 obtained from Zimmermann, and a similarly named bac- 

 terium from Krai, and a bacterium isolated during the 

 summer of 1894 from the well of the local fort. 



A beautiful chromogenic culture obtained in 1898 from 

 Hohnl (Prague) corresponds entirely wdth the description 

 except that the liquefaction was prominently punched-out 

 in appearance and it did not stain by Gram's method. 

 Also, it seems to us, from a study of the literature, that it 

 is scarcely possible to differentiate a Bacillus violaceus 

 Laurentius (Lustig, p. 103), cultivated from the water of a 

 filter basin of Lawrence, a Bacillus violaceus Mac6 (Ann. 

 d'hygiene, 1887), and the Bacillus violaceus (Lustig, p. 

 75), from tap-water of Berlin and London. The latter, 

 according to Voges, is identical with the Bacillus lividus 

 of Plagge and Proskauer (Z. H. ii, 463), except that the 

 latter is differentiated from the violaceum by growing less 

 well upon potato and by rapid liquefaction. All these 

 characteristics, as follows from what has already been said, 

 are not sufficient for determining a separation of species. 

 Also closely related is the Bacillus membranaceus 

 amethystinus (Eisenberg, 1891, 421), cultivated by 

 JoUes from well-water. It produces large violet pel- 

 licles upon gelatin and is non-motile. Germano likewise 

 cultivated a membrane-forming organism (C. B. xii, 516), 

 which he named the Bacillus membranaceus amethyst- 

 inus mobilis. It agrees with the preceding except in 

 being motile. Also here it is probable that two identical 

 varieties are found, the one motile, the other non-motile. 

 This is in accord with Ward's discovery of an organism 



