15 



changed except for orange pigment at the surface. No gas is pro- 

 duced ; growth but no pigment occurs at 37 . It differs very little 

 from B. rubric us, i. e., only in bouillon and in milk. 



B. lactis erythrogenes (Hueppe). 



It was long ago observed in dairies that so-called bacterial 

 44 red milk" occured in one of two ways ; either red flakes appeared 

 on its surface, or the whole mass of liquid was colored red. The 

 former phenomenon is ascribed to B. prodigies us; the second 

 is usually due to an organism discovered in 1886 by Hueppe, 

 and described in 1889 by Grotenf eldt, (63) as B. lactis 

 erythrogenes. This organism, according to Grotenf eldt, 

 is a small rodlet, 11,4/4 long, non- motile and sporeless. 

 The gelatin colonies are small, round, and at first grey- 

 white, later yellow, as the gelatin becomes liquefied. Around 

 them the gelatin has a rose tint. A gelatin stab cul- 

 ture liquefies slowly from the top. After 1012 days the 

 liquefied portion is red, with a yellow sediment, while the solid 

 portion below is a weak rose color. The growth on potato 

 and agar is yellow, and after 6 8 days at 37 C, the pigment be- 

 comes a deep golden color. Bouillon is cloudy and yellow. Milk 

 undergoes a slow precipitation of casein, leaving a clear serum 

 which becomes blood red; the reaction is alkaline. The organism 

 is not pathogenic; the cultures are characterized by a sweet odor. 



My culture of B. lactis erythrogenes, from Krai, agreed 

 closely with this description. Another culture, isolated in Novem- 

 ber 1901 from Mississippi River water, corresponded to the Krai 

 culture in all characters except that the color of the yellow pig- 

 ment was a shade lighter, with a tendency to appear much later 

 in the growth. The following details may be added to the descrip- 

 tion of these cultures: Growth on agar is moist, luxuriant and 

 yellow, while the medium becomes rose colored as in gelatin, and 

 even wine red. The yellow growth on potato shows often a slight 

 pink tinge, the potato becoming dark and discolored. Blood serum 

 not liquefied; no gas in sugar bouillon; no development without 

 free oxygen ; development with pigment at 37 C ; nitrates reduced 

 to nitrites. The sweet odor of the cultures is very noticeable. 



B. rubefaciens (Zimmermann). 



Isolated from the Chemnitz water supply and described by 

 Zimmermann in 1890(67). Characterized by a rose red color 

 which diffuses throughout solid media such as gelatin or agar. 

 Morphologically, a thin rodlet, 1 1.6 u long, often in chains of 

 two or three. Actively motile, no spores. Gelatin colonies ap- 

 pear as minute white dots in 48 hours; under low power, pearly, 

 thinner at the edge, which is well defined, finely granular. In gelatin 

 stab, small spherical white colonies occur along the needle track, 

 giving a characteristic appearance. The surface colony is yellowish, 

 and in old cultures a red tinge may be seen in the medium. No 



