242 



ESSENTIALS OF BOTANY 



the contents with air containing living bacteria, no putre- 

 faction can occur. Canned goods may be kept unspoiled 

 for an indefinite number of years, not because all the 



Fig. 169. Bacteria stained to show Cilia. 



A, Bacillus subtilis, found in hay infusions; B, Spirillum umluhi, found 

 in water containing decaying fish, algse, etc. ; C, species of Pseudomo- 

 nas; B, Planococcus citreus, which forms yellow patches on various 

 substances; E, Bacillus typhi, the cause of typhoid fever; F, Micro- 

 spira comma, the cause of Asiatic cholera. 



air has been driven out of the cans, but because they and 

 everything in them has been sterilized by heat. Bacteria 

 in the active growing condition cannot live if exposed 



