PRODUCTS OF BACTERIAL GROWTH 127 



New Products 



Decomposition Products. When a house falls to pieces 

 after burning, a mass of debris is left lying in the old cellar. 

 So, when the chemical molecule is broken to pieces, as 

 described above, there will remain certain fragments of 

 the original molecule. Although really fragments of the 

 original substances they are quite different in nature from 

 the original material. They are known as by-products of 

 decomposition, or simply as decomposition products. When- 

 ever bacteria grow in a mass of food, destroying the 

 chemical nature of the food molecules, there is sure to be 

 produced a variety of materials representing the debris 

 from the destruction of the molecule. These materials 

 are by-products of decomposition and are always of a 

 nature quite different from the original food substance. 

 They are, as a rule, simpler in their chemical nature than 

 the original food, and are quite different in their physical 

 characters. 



From the original food, which may have been a partly 

 solid material, like a bit of meat, there arises as the result 

 of its destruction a number of these by-products, some of 

 which are in the form of gases and pass off into the air, 

 some of which are more or less liquid and remain behind 

 in the food mass. Others are easily soluble in water and 

 dissolve in the liquids of the food. Thus the food material 

 is almost sure to soften gradually and to become of a more 

 or less fluid nature. There is likely to be a considerable 

 variety of these by-products, some of them having new 

 odors and tastes. The new materials give to the food 

 mass as it is consumed by bacteria wholly new flavors ; 



