218 AGEICULTUEAL AND INDUSTEIAL BACTEEIOLOGy 



butyric acid. Among these are the organisms which pro- 

 duce tetanus or lockjaw, blackleg in cattle, gaseous gan- 

 grene and malignant edema. Certain of the bacteria most 

 important in bringing about putrefaction, such as Clos- 

 tridium putrificum, are likewise important. The organism 

 most commonly associated with butyric fermentation is 

 Clostridium butyricum. It is a rod-shaped. Gram-positive, 

 motile rod, producing spores, the cell during sporulation 

 becoming swollen or spindle-shaped. It can be grown in 

 ordinary culture media under anaerobic conditions. In the 



Fig. 52. — Crystals op calcium oxalate in medium in which 

 Aspergillus is growing 



presence of sugars, particularly of dextrose, abundant gas 

 formation and development of butyric acid occurs. The 

 process is soon halted, however, by the increasing acidity of 

 the solution unless some means is taken to neutralize the 

 developing acid by the presence of some base, such as 

 calcium carbonate. 



The Clostridium pectinovorum has been repeatedly 

 isolated from hemp during the process of retting by the wet 

 method. This organism has markedly developed the power 

 to dissolve the pectin from the middle lamella joining the 

 cells and bundles of bast fibers together in the stems of 

 plants. Pure cultures have been used to some extent in 

 facilitating the process. 



