QUALITATIVE BACTERIOLOGICAL ANALYSIS. 153 



Gelatine-plate Cultures. The growth is characteristically 

 rapid. The deep colonies quickly reach the surface, to form 

 saucer-shaped areas of liquefaction ; from the edge of these 

 processes may be given off which are almost of the nature 

 of " swarming islands." In the areas of liquefied gelatine the 

 bacteria may be gathered in clumps so as to give rise to a 

 mottled appearance. Under a low power the surface colonies 

 may be almost completely translucent and of an irregular star- 

 shaped form ; but soon circular areas of liquefied gelatine are 

 produced, in which the extraordinarily rapid movement of the 

 individual bacilli can be clearly watched. 



Gelatine-stab. Rapid liquefaction takes place in the form of 

 a funnel. The liquefied gelatine has a greyish-white flocculent 

 appearance, due to aggregation of little masses of bacteria. 



Gelatine-streak. The growth is not characteristic owing to 

 the rapid liquefaction. 



Gelatine-shake Cultures. No gas bubbles are formed. 



Agar-streak. In twenty-four hours at 37 C. a dirty, 

 yellowish-white film has covered nearly the whole surface of the 

 agar. The spreading edge may be lobed or fissured. The film 

 darkens in colour and becomes wrinkled. 



Potato Cultures. The growth is extremely characteristic. In 

 twenty-four hours at 37 C. the whole surface of the potato is 

 covered with a thick, greyish-white moist skin, which is thrown 

 into multiple folds, creasings and wrinkles. The colour 

 rapidly changes from greyish -white to yellow and then to 

 brown. 



Broth Cultures. The growth at 37 C. is characteristic even 

 in twenty-four hours. A greyish-white wrinkled film is formed 

 at the surface, and the liquid below is nearly quite clear. Later 

 the film thickens and acquires a reddish-brown colour; the 

 liquid below, which remains nearly quite transparent, also takes 

 on a reddish-brown colour. 



Litmus-milk. In forty-eight hours there is no clot, but the 

 milk is rapidly becoming transparent ; in seventy-two hours 

 the whole of the contents of the tube are semi-transparent and 

 of a dirty yellowish colour. On gently shaking the tube, the 

 liquid assumes a crushed-strawberry colour. 



Indol. No indol is formed. 



