386 J. RUSSELL ESTY 



days' incubation. The colonies are much larger in media con- 

 taining sugar than on plain agar. The size of colonies on glucose- 

 liver-agar varies greatly from minute nearly microscopic colonies 

 on thickly seeded plates to those measuring from 3 to 5 mm. 

 on plates with few colonies. 



The colonies in stab cultures, and those deep in the agar on 

 plates, appear as spheres or ovals, generally more or less flattened 

 with irregular contours, the irregularity being due to little 

 feathery projections or prongs from the surface of the colonies. 

 The colonies are very firm, and retain their shape and consistency 

 when touched with a needle. 



2. Gelatin. Gas is formed in ordinary nutrient gelatin (re- 

 action + 1) neutral glucose-gelatin and neutral glucose-liver- 

 gelatin. The gas production in these media varies, nutrient 

 gelatin showing the least and glucose-liver gelatin the most 

 abundant production. Growth occurs in all three at 20° and 

 37°, the glucose-liver cultures developing more rapidly and 

 abundantly than nutrient gelatin cultures. 



A slight initial softening is observed in the 20° cultures, due 

 to the peptonization of the gelatin at the top of the stab; later 

 the growth settles downward along the line of puncture, until 

 in some cases the entire medium liquefies. 



S. Broth. Growth occurs under strictly anaerobic conditions 

 in sugar-free broth, and in broth containing glucose, sucrose, 

 maltose, lactose, dextrin, starch, liver and inulin. The gas is 

 so abundant in the sugar broth that small bubbles of gas rise 

 to the surface and accumulate to form a "foamy" layer, present- 

 ing a "steaming" appearance. At 37° growth takes place in 

 two or three hours, the clear broth first becoming cloudy with 

 abundant sediment at the bottom of the tube. When gas for- 

 mation starts it goes on with great rapidity for about twenty-four 

 hours in plain broth and still longer in sugar broth. After the 

 fermentation ceases the diffuse cloudiness disappears and the 

 sediment settles in the course of a short time, rendering the cultures 

 clear and transparent. The sediment is white, uniform and flaky 

 and more abundant in sugar broth than in plain broth. If the 

 sediment is disturbed, it floats in a viscid thread or cloud produc- 



