266 DECOMPOSITION 



of flax and other fiber-producing plants. Pectinase by its 

 activities releases the fibers for weaving or other mechan- 

 ical treatment. In practice, the fibers of flax and other 

 textile materials are obtained on a commercial scale by a 

 process of rotting in water known as retting. This is 

 accomplished by one or more species of bacteria living in 

 water, the desired action of which is the production of 

 pectinase which dissolves the fiber-cementing material. 

 However, as general decay accompanies this specific ac- 

 tion, the strength and color of the fiber are impaired and 

 the process is to this extent objectionable. Attempts have 

 been made to carry on retting by means of pure culture, 

 and it is conceivable that under certain conditions at 

 least the product may be improved in this way. It is 

 also conceivable that autolysis may be made to yield the 

 desired result without corresponding injury. In these 

 fermentations, as in the others above described, the cell- 

 w^all materials are digested by being converted into sugars 

 which furnish the fungi, bacteria, or other organisms with 

 the food which they require. 



Decomposition of Fats and Oils is accomplished by 

 the action of organisms. Thus, for example, in butter 

 which we eat and butter which we keep too long, the 

 enzyms are lipases. These, whether formed in the intes- 

 tine or by bacteria, break down the fats to glycerine and 

 fatty acids. These in turn may be further broken down 

 or oxidized in the cells, until finally CO2 and H2O are the 

 end products. Corresponding amounts of energy are 

 liberated in the successive stages of decomposition. 



Decomposition of Nitrogenous Waste. — It has 

 been shown (Chap. VIII) that some of the nitrogenous 

 food and some of the nitrogenous material of the animal 

 body are broken down in basic metabolism and thrown 

 off, being excreted mainly by the kidneys in the form of 

 urea. This partly oxidized compound serves as food and 

 fuel for certain species of bacteria, which further oxidize 

 it to ammonia and CO2. The liquid organic nitrogenous 



