On agar slant the growth appears first as a white smooth moist 

 layer, in 24 hours becoming bright red. In three or four days a 

 green fuchsin-like luster appears on the surface. Old cultures grow 

 darker in color (cf. table in section on pigment). 



Potato. This was the culture medium used by the early 

 investigators. The growth and pigment production are here most 

 beautiful, particularly if the potato is fresh and slightly acid. A 

 white line appears in twelve to eighteen hours, which rapidly turns 

 red. The growth is luxuriant and the surface takes on a green 

 metallic luster in a few days, while the red color spreads over the 

 potato by means of the film of moisture. If the potato is dry, 

 growth and pigmentation are limited to the needle track, and the 

 superficial green appears as an abundant, dull, granular layer. 



Blood serum. The growth is like that upon agar, but 

 slighter. The medium later undergoes liquefaction. 



Bouillon. Ordinary neutral bouillon becomes cloudy in 12 

 to 18 hours. Later a ring of red color appears at the surface and 

 a flocculent red and white sediment accumulates. The surface 

 sometimes has a slight red pellicle and the whole liquid may be 

 tinged red. 



Milk. In milk the red color appears at the surface, the pig- 

 ment, according to Fliigge (3) and Migula (10), adhering to 

 the fat droplets. A soft solid coagulum^s formed in 48 hours by 

 the simultaneous formation of "Milchsaure und Labferment" 

 (Gorini (41)). In ten days the coagulum shrinks to half its size, 

 leaving a clear watery serum. Little or no peptonization takes 

 place. 



Gas production. The question of the production of gas 

 in sugar solutions by B. prodigiosus has occasioned some dis- 

 cussion. Liborius (34) (1886) described gas development by 

 B. prodigiosus in dextrose gelatine. Schottelius (35) (1887) 

 stated that this organism possessed in a marked degree the power 

 of converting sugar solution into alcohol and C0 2 , a statement 

 which has been embodied in Fraenkel's text book (4). S c h e u r - 

 len, however, disagrees with this conclusion of Schottelius. 

 He found that, in a peptone solution to which 2 % sugar had 

 been added, a gas bubble appeared upon inoculation with B. pro- 

 digiosus, did not increase, and, because of its absorption by 

 NaOH, was proved to be C0 2 ; but he believed this to be the 

 result of the action of succinic acid (which he had shown to be 

 a product of B. prodigiosus in potato culture) upon the sodium 

 carbonate used to neutralize the bouillon. When he tried a sugar 

 peptone bouillon neutralized by sodium-phosphate, or one to which 

 no alkali had been added, or an asparagin-sulphate-phosphate sugar 

 solution, he obtained no gas bubble. The bubble appeared, however, 

 when B. prodigiosus was grown in any medium which had 

 been neutralized by Na 2 C0 8 , even when the medium contained no 

 sugar. He also obtained gas without the presence of B. pro- 

 digiosus merely by the addition of a little succinic acid to the 

 medium. Ritter (47) (1900) confirms Scheurlen, and says 



