294 J. S. LAWRENCE AND W. W. FORD 



Litmus glucose agar colonies. Superficial colonies are thick, 

 highly refractive, waxy, with entire edges or spreading with 

 irregular edges. They soon become dry and wrinkled in the 

 center. Under low power opaque with entire edges. Deep 

 colonies are punctiform, round, oval or irregular with crenated 

 margins. Under low power opaque with irregular margins. 

 Medium acidified at first then turned alkaline. 



Gelatin. Stab gives cup-shaped and surface liquefaction with 

 heavy scum production. 



Gelatin colonies. Colonies round with highly refractive cen- 

 ters occasionally showing beautiful concentric rings. Under 

 the low power the colonies have a granular appearance. Medium 

 liquefied. 



Broth. Tiu-bidity within 24 hours and scum formation usually 

 on second day. Medium gradually clears. 



Peptone. Turbidity within 24 hours. Thin fragile scum 

 after the lapse of several days. Medium gradually clears. 



Potato. Characteristic appearance. Thick, white, gray or 

 pink folds or wrinkles are formed within 24 to 48 hours often 

 covering entire cut surface of potato. Later these folds dry 

 down to a brown, reticulate mass. Potato usually discolored. 



Litmus milk. Slight clearing of the milk just beneath the 

 cream layer usually appears in 24 hours. This reaction rapidly 

 intensifies with the production of a clear fluid colored* deep 

 Chinese-blue or purple. No acid production or coagulation. 

 As the milk gets older complete peptonization occurs with the 

 formation of a clear amber-colored fluid. 



Blood serum. Thin dry abundant growth usually smooth, 

 but sometimes wrinkled and pink. Growth later becomes 

 moist and gives a suggestion of liquefaction. 



Fermentation tubes. Glucose. Luxuriant growth in bulb gradu- 

 ally extending into the closed arm. An abundant scum is 

 formed which may be quite wrinkled. Reaction acid. 



Saccharose. Growth luxuriant in bowl but scanty in arm. 

 Very thin scum may be formed after several days, but this may 

 be lacking. Reaction varies from slight to marked acidity. 



Lactose. Abundant growth in bowl with late scum produc- 

 tion. No growth in closed arm. Reaction alkaline 



