MICROCOCCUS PKODIGIOSUS. 137 



regards form and conditions of growth, may in certain cases 

 produce the same colouring matter. (4.) Most of the species 

 apparently producing the same colouring matter, and also analogous 

 in other respects, can be differentiated by the reactions of their 

 colouring matter. 



87. Microeoeeus Prodigiosus. 



This being the oldest known chromogenic bacterium, will be 

 dealt with first. 



Many a victim of the proceedings taken against witchcraft 

 during bygone centuries must have been consigned to the stake 

 on the charge of having fabricated the blood-red spots that were 

 occasionally found developed on the Host, and which filled the 

 credulous mind of the masses with horror; and even in 1819 the 

 entire province of Padua was set in a commotion by the frequent 

 appearance of such spots and drops on various articles of food. 

 This red, slimy coating was examined by SETTE (I.), who re- 

 cognised it as endowed with vitality and named it Zoogalactina 

 imetrofa. A small quantity applied to still unaltered food-stuffs, 

 <fec., sufficed to produce red spots on these latter. This phenomenon 

 was first more closely investigated in 1848, when it was of frequent 

 occurrence in Berlin. Chr. Ehrenberg studied the spots and 

 drops, and found them to consist of minute oval cells 0.5 to 

 i.o ft in length; and bearing in mind their form and observed 

 powers of locomotion, he classified this wonderful organism as a 

 new species of his genus Monas, and called it Monas prodigiosa, a 

 designation subsequently changed by Cohn to Microeoeeus pro- 

 digiosus. As this microbe (mostly appearing as approximately 

 spherical cells) will, under certain conditions of environment, 

 assume an elongated form, it is also frequently named both 

 Bacterium prodigiosum and Bacillus prodigiosus. as was done by 

 Flugge in his handbook. These names, therefore, indicate one and 

 the same species of fission fungus, and are also synonymous with the 

 older names Palmella prodigiosa and Bacleridium prodigiosum. 



This fission fungus excretes a peptonising enzyme, and conse- 

 quently liquefies the gelatin medium. A temperature of 25 C. is 

 the most favourable one for its growth, and it thrives most luxuri- 

 antly on boiled potatoes, the formation of trimethylamine becom- 

 ing at the same time apparent. Starch paste, boiled rice, boiled 

 egg-albumin, boiled carrots, boiled meat, milk, and many other 

 food stuffs, form suitable media for this microbe, which, however, 

 will not develop on raw potatoes, raw meat, or uncooked steeped 

 rice. It is therefore evidently a true saprophyte, occurring only 

 in defunct or destroyed and converted nutrient media. When 

 cultivated in thinly fluid solutions it exhibits as was established 

 by SCHOTTELIUS (I. ) brisk powers of locomotion. 



The red colouring matter, which is produced in presence of 



