BACILLUS AEROGENES CAPSULATUS. 467 



make their appearance in plain agar as well as in sugar- 

 agar, though, of course, less plentifully. They first ap- 

 pear in the line of growth; afterward throughout the 

 agar, often at a distance from the actual growth. Any 

 fluid collecting about the bubbles or at the surface of the 

 agar-agar may be turbid from the presence of bacilli. 

 The gas-production is more abundant at incubation- than 

 at room-temperatures. 



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-pro- 

 duction. 



In its growth the bacillus produces acid in considerable 

 amount. 



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 very rapid in its 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 bouillon becomes strongly 

 acid. 



In milk the growth is rapid and luxuriant under 

 anaerobic conditions, but does not take place in cul- 

 tures 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. 



The bacillus will also grow upon potato when the tubes 

 are enclosed 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 froth. After complete absorption of the oxygen a 



