APPENDIX. 433 



shaped liquefaction area along the line of the needle, and in the gelatine 

 that still remains solid, clear bubbles of gas may be seen. The organism 

 that produces these changes is a very minute, exceedingly motile rod. 



iv. Giving rise to a strong putrefactive odour. 



( i ) Liquefying bacillus of Water ( Verflussigender bacillus of ' the Germans'). 

 Very rapidly forms round colonies with smooth walls ; in the centre of 

 the liquefying area is seen a white viscid mass ; after a time an offensive 

 putrefactive odour is given off; in a gelatine tube puncture cultivation 

 there soon appears along the track of the needle a white granular mass, 

 which is followed by a funnel-shaped area of liquefaction; short, somewhat 

 thick rods with rounded ends. 



B. Colonies or nutrient substratum coloured. 



a. Colouring matter, red. 



b. Colouring matter green, see p. 434. 



c. Colouring matter violet, see p. 434. 



a. Colouring matter red. 



(1) Bacillus prodigiosus (Micrococcus prodigiosus, Monas prodigiosus). 

 Grows very rapidly on plates at from 20 to 22 C., in the deep layers as 

 grey points, superficial growths small grey rounded colonies, about I mm. 

 in diameter ; these sink into the gelatine, which is rapidly liquefied, but 

 remains quite clear ; under the low power deep colonies are seen to be 

 rounded or oval, and to have sharp outlines, but those at the surface are 

 granular and have an irregular outline ; when liquefaction has set in a 

 beautiful red colour makes its appearance, but this is best seen on agar 

 cultivations, where there is free access of oxygen to the growing organism ; 

 on potatoes a beautiful moist blood-red layer is formed, which is perfectly 

 characteristic ; the bacilli themselves are colourless ; the pigment is in- 

 soluble in water, soluble in alcohol ; occurs as egg-shaped non-motile cells, 

 about i/tt in diameter, especially when the liquefaction is rapid ; sometimes, 

 when the growth is slower, the organism is distinctly rod-shaped, or it may 

 occur in the form of short threads. 



(2) Bacillus indicus ruber. Found in the contents of the stomach of a 

 monkey. Was the organism with which Koch made some of his experi- 

 ments in connection with the destruction of micro-organisms in the alimen- 

 tary canal. The colonies on plates are first of a yellow colour, and have 

 a wavy outline ; the superficial growths bring about the liquefaction of the 

 gelatine, this first appearing as a little zone round the colony, and giving 

 rise to a liquefied funnel-shaped area ; in gelatine needle cultures a waxy 

 or brick-red colour forms at the surface, but along the track of the needle 

 the growth is somewhat grey or white j on potatoes forms a localized brick - 

 red or waxy layer ; grows best at a temperature of about 35 C., as a very 

 thin and short bacillus with rounded ends ; injected in large quantities into 

 rabbits it causes death from diarrhoea in from three to twenty hours. 



(3) Red bacillus. Found in water. On plates forms finely granular 

 colonies with smooth surfaces; red coloured points accumulate in the centre 

 of small liquefied areas in gelatine tubes, as the gelatine is gradually 

 liquefied, and a brownish-red coloured mass sinks to the bottom ; grows on 

 agar-agar, potatoes, and blood serum with the same characteristic brownish- 

 red colour ; is an exceedingly motile bacillus of medium size, and with 

 somewhat truncated ends, sometimes united to form long threads. 



29 



