BACTERIA IN INDUSTRIES 



405 



There are many different 

 bacteria which grow in milk. 

 A group attacks milk sugar 

 and produces lactic acid, 



A similar process takes place in preparing linen fibers. Linen 

 comes from the flax plant. If the flax is cut and thrown into pits 

 and kept damp, certain bacteria will decay 

 the cementing materials which hold the 

 tough, strong fibers together. These fibers, 

 when separated, are used for the manufac- 

 ture of linen. This process of obtaining the 

 fibers of flax is known as retting or rotting. 

 There is an artificial process of retting which 

 is not as successful as the natural water 

 process. The natural process is used in 

 Ireland and produces a fine grade of linen. which results m sourin g- 

 The artificial process, used in the United States, consists of an 

 acid treatment for loosening the fibers. It is much quicker than 

 the natural method, but less perfect, since the acid may roughen 

 the flax fibers. 



Bacteria are valuable in curing tobacco. The tobacco stalks 

 with the leaves are piled into great heaps or hung from racks and 

 allowed to sweat and then ferment at a fairly low temperature. 

 This gives to tobacco its special flavor. 



In tanning leather, the hides are soaked, scraped, and limed or 

 treated with acids to remove the hairs. The lime is removed, 

 and the hides are put into solutions of tan- 

 bark. During these processes, certain bac- 

 terial fermentations take place, which make 

 'the leather soft and pliable. 



Bacteria in agriculture. Large quantities 

 of the nitrates from the soil are built into 

 proteins and protoplasm by the plants, 

 in fruit juices bacteria When these plants are removed, they take 



change alcohol to acetic 



ad. with them the nitrogen in the form of 



protein and protoplasm. The nitrogen of the soil would be 

 exhausted in a comparatively short time if there were no ways 



