FUNCTIONS OF SAPROPHYTIC BACTERIA 35 



other aromatic bodies of organic character and origin; the 

 spoiling of wine; the disintegrations incidental to the 

 manufacture of hemp products; the old method of making 

 indigo; the natural and artificial methods for the destruction 

 of the organic waste encountered in polluted waters and 

 sewage and the transformations of dead organic matter in 

 the soil are all illustrations of these well-known phenomena. 

 In a number of commercial lines constant use is made of 

 these bacterial activities. This is conspicuously seen in • 

 the manufacture of butter and cheese where the excellence 

 of the products is due to the peculiar flavors caused by 

 bacterial growth in the raw materials. Before synthetic 

 methods became so generally in use bacterial activities were 

 largely employed in the manufacture of the organic acids. 



In addition to the foregoing a number of saprophytes 

 have the specific property of producing beautiful pigments, 

 red, yellow, orange, pink, violet, green, etc. This group of 

 " chromogens" as they are called have doubtless other func- 

 tions in the great laboratory of nature, the soil, where they 

 are commonly found, but color production is the most 

 obvious. 



Another group — the " photogens" or photogenic species 

 have the remarkable ability to produce luminosity in the 

 substances in or on which they exist. It is to the activity 

 of this group that the phosphorescence sometimes seen in 

 decayed wood, in rotten fish and other flesh is attributable. 

 How it is done is a mystery, just as is the means by which 

 the fire-fly and the glow-worm emit their tiny sparks of light. 



Another group have as the end products of their activities 

 those evil smelling bodies by which putrefaction is charac- 

 terized, these are the so-called "saprogenic" species. 



Others have as their most interesting functions the power 



