86 AGRICULTURAL BACTERIOLOGY 



koff, the Russian bacteriologist, also asserts that what are 

 usually regarded as symptoms of old age in man are due to 

 the gradual replacement of the normal flora by a harmful 

 one. 



Retting of fiber plants. In the preparation of the fibers 

 from such plants as hemp and flax, it is necessary to decom- 

 pose the binding substances that hold the fibers together. 

 These bodies a.re carbohydrates and are known as pectins. 

 In the rotting or "retting" process, it is essential that the 

 cellulose fibers shall not be acted on so as to weaken their 

 strength. In the case of flax, the straw may be immersed 

 in water for a short time, or it may be allowed to lie on the 

 surface of the ground. The bacteria and molds quickly de- 

 compose the pectins, and by breaking the straw into short 

 pieces the fiber may then be freed from the binding mater- 

 ial. In some parts of the world certain streams have been 

 found to be very favorable for the retting of flax. The river 

 Lys in Belgium is a famous place for flax retting. The 

 content of the water in pectin-decomposing organisms is sup- 

 posed to be the explanation of the favorable action of this 

 river. Efforts have been made to isolate pure cultures of 

 the pectin-fermenting organisms, and to use them in the 

 retting of flax in tanks, instead of exposing it in natural 

 waters. Pectin-decomposing organisms play an important 

 role in the spoiling of fruits and vegetables. 



Oxidation of hydrogen and methane. Hydrogen and 

 methane are commonly formed in the decomposition of car- 

 bohydrates. Neither the hydrogen nor the carbon is here 

 available for the green plant. Bacteria have been found 

 that are able to oxidize such energy-containing gases, form- 

 ing the ultimate decomposition products, carbon-dioxide 

 and water. 



