60 



VKI'l-.R] XAR V I'AT 1 1 OIJ )G Y. 



— Ilacilli:?, Tetac; 



in manure piles, alfalfa, Iiay and x-aritais Lj'rains in the slacls: is 

 thought to be the result of bacterial action. In the above sub- 

 stances, the contained moisture favors the growth of bacteria and 

 the growth of zymogenic bacteria is always dependent upon 

 chemic changes in which complex compounds are reduced to 

 simpler ones. Such chemical changes are accompanied by the 

 evolution of heat. In all fermentation, in which the substances 

 acted upiin are converted into simple compounds, heat is liber- 

 ated. Light or phosphorescence ma\' be produced bv bacteria. 

 The phosphorescence of decayed \\oiid, ocean water, flesh, etc., 

 ma\' accompany the growth of li.ght jiniducing bacteria. Light is 

 a form of energv and bacterial light or phosphorescence is the 

 result of the conversion of some other form of energy usually 

 kinetic euerg},', into ether \'i1)rations or light. The production 

 of heat and light are of little importance in comparison with 

 other bacterial products and activities. 



Pigments of various kinds are produced by several different 

 species of bacteria. These pigments may l)e an excretion or a 

 secretion or they may possibly represent synthetic extracellular 

 products or enzymotic by-products. The importance of bac- 

 terial pigments is largely confined to the discolorizatiou of food 

 substances. Thus the Micrococcus roseus. Bacillus pnidigiosus, 

 and Bacillus erythrogenes, produce a red pigment in milk. The 

 red pigment in the milk is sometimes mistaken for bloody milk. 



