48 THE STORY OF THE BACTERIA. 



the milk which is stored in special rooms. 

 This occurrence, for a long time a disagreeable 

 and costly mystery, is now known to be due to 

 a tiny bacterium of the genus Bacillus, which, 

 floating about in the air with the dust, from 

 time to time infects rooms, and, falling into 

 the milk, grows there, producing the blue 

 coloring matter. 



Sometimes milk gets red instead of blue, 

 and then the change is due to another form of 

 bacteria floating with the dust. Bread, too, 

 may become infected in the same way, and the 

 dough set aside in bake-shops overnight to 

 rise has not infrequently been found in the 

 morning resplendent with colors which fairly 

 rivalled those of the rising sun. 



There is a species of bacteria in every good 

 collection, and a veritable Nestor among the 

 forms known to man, which has a curious 

 ecclesiastical history. Among all the innu- 

 merable natural phenomena which, by their 

 striking character, infrequent occurrence, and 

 lack of apparent cause, were in early times 

 relegated to the domain of the supernatural, 

 none perhaps was more strange and uncanny 



