USE OF BACTERIA IN THE ARTS. 41 



CHAPTER II. 



MISCELLANEOUS USE OF BACTERIA IN THE ARTS. 



THE foods upon which bacteria live are in 

 endless variety, almost every product of animal 

 or vegetable life serving to supply their needs. 

 Some species appear to require somewhat definite 

 kinds of food, and have therefore rather narrow 

 conditions of life, but the majority may live upon 

 a great variety of organic compounds. As they 

 consume the material which serves them as food 

 they produce chemical changes therein. These 

 changes are largely of a nature that the chemist 

 knows as decomposition changes. By this is 

 meant that the bacteria, seizing hold of ingre- 

 dients which constitute their food, break them to 

 pieces chemically. The molecule of the original 

 food matter is split into simpler molecules, and 

 the food is thus changed in its chemical nature. 

 As a result, the compounds which appear in the 

 decomposing solution are commonly simpler than 

 the original food molecules. Such products are 

 in general called decomposition products, or some- 

 times cleavage products. Sometimes, however, the 

 bacteria have, in addition to their power of pull- 

 ing their food to pieces, a further power of build- 

 ing other compounds out of the fragments, thus 

 building up as well as pulling down. But, how- 

 ever they do it, bacteria when growing in any 

 food material have the power of giving rise to 

 numerous products which did not exist in the 

 food mass before. Because of their extraordi- 

 nary powers of reproduction they are capable of 

 producing these changes very rapidly and can 



