SYSTEMATIC AND DESCRIPTIVE. l8l 



in a screw-like manner. In the next stage of 

 development the rods cease to move, and become 

 swollen with granular contents. One extremity 

 develops an enlargement, giving the rod the 

 appearance of a pin. The spore formed by the 

 contraction of the plasma in the swollen end finally 

 becomes globular. The vibrios appear in vegetable 

 infusions, causing fermentation of cellulose. 



Genus VI. Clostridium. 



Clostridium butyricum, Prazmowski (Bacillus 

 amylobacter Van Tieghem ; Bacillus butyricus. 

 Bacillus of butyric acid fermentation). Rods of 

 3 10 \L long, and under i p wide, often indis- 

 tinguishable from bacillus subtilis. They grow out 

 into long, apparently unjointed threads. They are 

 mostly actively motile, but also occur in zooglcea. 

 The rods and threads are sometimes slightly bent 

 like vibrios. They are anaerobic. The shorter rods 

 as a rule swell in the middle, becoming ellipsoidal, 

 lemon or spindle-shaped ; the long rods, and some- 

 times the short ones, swell at one end ; in either 

 case ellipsoidal spores are developed. 



If they be cultivated in nutrient gelatine, the 

 medium is liquefied, and a scum formed on the 

 surface. They grow best between 35 and 40^ C. 

 The spores are widely distributed in nature, and 

 grow readily on fleshy roots, old cheese, etc. They 

 convert the lactic acid in milk into butyric acid, 



