SYSTEMATIC AND DESCRIPTIVE. 24 1 



Bacterium rubrum, Frank. Minute motile 

 rods, singly, in twos, and fours. They were 

 observed on boiled rice, where they develop a 

 brick-red pigment. 



Bacterium prodigiosum (Micrococcus prodigi- 

 osus, Bacillus prodigiosus* " Blood-rain" " Bleeding 

 host"}. Very short rods with rounded ends, and 

 thread- forms, '5 i //, in width, forming at first 

 rose-red, and then blood-red zoogloea. They grow 

 luxuriantly when cultivated on sterilised potatoes 

 (Plate IX., Fig. i), and on the sloping surface of 

 nutrient agar-agar (Plate II., Fig. 3). They 

 appear occasionally on bread, boiled rice, and 

 starch-paste, and more rarely on boiled white of 

 egg and meat. Milk sometimes becomes coloured 

 blood-red by the growth of this fungus, an appear- 

 ance formerly attributed to a disease of the cow. 



In Paris, in 1843, the fungus was peculiarly 

 prevalent, attacking especially the bread produced 

 in the military bakehouses. 



The cells themselves are colourless. The 

 colouring matter resembles fuchsine ; it is in- 

 soluble in water, but soluble in alcohol. The 

 addition of acids changes it to a carmine red, and. 

 of alkalies to a yellow colour. 



Bacterium luteum (Bacillus luteus, Fliigge). 

 Short immotile rods. Colonies irregular in form, 

 appear brownish under a low power, but macro- 

 scopically yellow. In test-tube cultivations they 

 form a yellow growth without liquefying the 



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