Cultivation 381 



spheres or ovals, more or less flattened, with irregular con- 

 tours, due to the presence of small projecting prongs, which 

 are quite distinct under a lens. The colonies may appear as 

 little irregular masses with projections. 



After several days or weeks, single, well-shaped colonies 

 may attain a large size and be surrounded by projections, 

 either in the form of little knobs or spikes or of fine branch- 

 ings hair-like or feathery. Their appearance has been 

 compared to thistle-balls or powder-puffs and to thorn-apples. 

 When the growth takes place in the puncture, the feathery 

 projections are continuous. Bubbles of gas make their ap- 

 pearance in plain agar as well as in sugar-agar, though, of 

 course, less plentifully. They first appear in the line of 

 growth; afterward throughout the agar, often at a distance 

 from the actual growth. Any fluid collecting about the bub- 

 bles or at the surface of the agar-agar may be turbid from 

 the presence of bacilli. The gas-production is more abun- 

 dant at 37 C. than at the room temperature. 



The agar-agar is not liquefied by the growth of the bacillus, 

 but is often broken up into fragments and forced into the 

 upper part of the tube by the excessive gas-production. 



In its growth the bacillus produces considerable acid. 



Bouillon. In bouillon growth does not occur in tubes 

 exposed to the air, but when the tubes are placed in Buchner's 

 jars, or kept under anaerobic conditions, it occurs with abun- 

 dant gas-formation, especially in glucose-bouillon, with the 

 formation of a frothy layer on the surface. The growth is 

 rapid in development, the bouillon becoming clouded in two 

 to three hours. After a few days the bacilli sediment and 

 the bouillon again becomes clear. The reaction of the bouil- 

 lon becomes strongly acid. 



Milk. In milk the growth is rapid and luxuriant under 

 anaerobic conditions, but does not take place in cultures 

 exposed to the air. The milk is coagulated in from twenty- 

 four to forty-eight hours, the coagulum being either uniform 

 or firm, retracted, and furrowed by gas bubbles. When 

 litmus has been added to the milk, it becomes decolorized 

 when the culture is kept without oxygen, but turns pink 

 when it is exposed to the air. 



Potato. The bacillus will also grow upon potato when the 

 tubes are inclosed in an anaerobic apparatus. There is a 

 copious gas-development in the fluid at the bottom and sides 

 of the tube, so that the potato becomes surrounded by a 



