406 BACTERIAL ORIGIN OF GUxMS OF ARABIX GROUP, 



impossible to pick up a fragment of the young colony with the 

 needle, the whole colony comes away. Microscopically, the colonies 

 are dark, very coarsely granular and crinkled. The margin is 

 indefinite on account of the consumption of the medium. The 

 deep colonies are granular and very irregular. The colour deepens 

 to a yellowish tint and the medium is slowly liquefied. 



Nutrient gelatine plate. — As on glucose-gelatine, but the 

 growth is poorer. 



Nutrient agar stroke. — A narrow, slightly raised, rough, dry, 

 glistening, lobular, yellowish-white growth forms at 30°; it 

 adheres firmly to the medium. The condensed water carries a 

 film from which the rough growth spreads upwards. 



Glucose-gelatine stroke. — A translucent white, very wrinkled, 

 rough, dry, dull growth, with an irregular margin is formed at 

 22°. A pit forms at the base of the stroke owing to the con- 

 sumption of the gelatine at the place of strongest growth. The 

 medium slowly liquefies and gravitates, producing an appearance 

 like the clear condensed water of an agar tube. The culture 

 coheres as a wrinkled skin. On gelatine the colour is always 

 white or very pale yellow; while on agar it changes from white 

 to yellow or bufi". 



Glucose-gelatine stab. — The stab becomes filiform-tuberculate. 

 The nail-head is sunken and a rough growth lines the surface of 

 the depression. Below the consumed medium the gelatine may 

 be slightly and locally liquefied. Gas bubbles are formed in the 

 medium; the gas formation is more pronounced in saccharose- 

 (^elatine, on plates of saccharose-potato agar, and in saccharose- 

 potato extract. 



Nutrient gelatine stab. — As in glucose-gelatine but poorer. 



Saccharose-potato agar stroke. — The appearance of the culture 

 depends upon the incubation temperature. At 30° in 24 hours 

 the growth is luxuriant and has spread over the greater portion 

 of the slope. It is undulating, much raised, glistening, granular 

 and apparently very slimy. The colour is the same as the 

 medium, viz., buff or very light oak. The condensed water has 

 been absorbed. In 48 hours the growth has spread entirely over 



