172 BACTERIA, YEASTS, AND MOLDS 



which occurs in the same material at an ordinary room 

 temperature. The common putrefactive bacteria grow 

 readily at high temperatures, but hardly at all at the 

 temperature of the ice chest. Other types of bacteria, 

 however, grow more readily at the lower than at the 

 higher temperatures, and meat or other food kept in the 

 refrigerator will in the course of time undergo a type of 

 decay due to the microorganisms favored by the low tem- 

 perature. This decayed meat appears somewhat different 

 from decayed meat at higher temperatures and has a dif- 

 ferent odor — a fact indicating a different type of putre- 

 faction. Certain peculiar kinds of decay are seen at these 

 low temperatures which are hardly found imder other 

 conditions. Occasionally, for example, fleshy foods, par- 

 ticularly those from salt water, like lobsters or fish, develop 

 a peculiar phosphorescence if kept in an ice chest. If exam- 

 ined in the dark they will be seen to glow with a somewhat 

 brilliant greenish light. This phosphorescence is due to the 

 development of certain very interesting kinds of bacteria, 

 and always appears if they grow luxuriantly at low tem- 

 peratures. They grow chiefly upon foods which contain 

 considerable salt, and hence particularly in marine foods. 

 They are more likely to be found in meat preserved in an 

 ice chest, since the more common decay produced by other 

 bacteria will at higher temperatures mask the growth of the 

 phosphorescent bacteria. It is not necessary to throw such 

 food away, since the phosphorescence does not appear to 

 render it unwholesome, and it may be eaten with impunity. 

 Although far less efficient than cold storage, the ice 

 chest is a means of preserving for a short time food that 

 would otherwise quickly spoil. Its efficiency depends 



