Minnesota Plant Life. 121 



when blood-spots have appeared upon the shew-bread, should 

 all be various results of bacterial growth. Such, however, is the 

 fact, and the whole may be comprehended upon returning to 

 the statement made in the opening of the chapter, that bacteria 

 are plants needing various foods and forming a variety of waste 

 products. The poisonous ptomaine produced by bacteria in ice- 

 cream may cause the death of an entire picnic-party ; the waste 

 products of a bacterial population of some ancient ocean, ag- 

 gregated in enormous quantities, may furnish work for thou- 

 sands of miners and lie at the foundation of great modern in- 

 dustries. 



In this brief account by no means all of the possibilities of 

 bacterial habits and characters have been exhausted, but enough 

 has been said to open up this most fascinating field of investiga- 

 tion and to show in what a multitude of ways bacteria touch 

 human life. 



