BACTERIOLOGY. 57 



presence of atmospheric air ; some physicians go a step 

 farther and advise the spraying of such wounds with 

 oxygen. In the preparation of some of the vaccines, 

 bacteria whose virulence has been reduced or destroyed 

 through subjecting them to unfavorable surroundings 

 are used for the inoculations, a form of vaccination 

 that is now being practised in typhoid fever and bubonic 

 plague. Because cold retards bacterial growth, is one 

 good reason for its use in inflammations. When the 

 urine is alkaline, as is usually the case in inflammations 

 of the bladder (cystitis), every effort is made to change 

 the reaction to acid and thereby make the urine an un- 

 favorable medium for the bacteria which cause the 

 cystitis. 



AGENTS HARMFUL TO BACTERIA. 



Agents which prevent the growth and activity of 

 bacteria without destroying them are called antiseptics; 

 those that destroy them, disinfectants or germicides. 

 Disinfection has as its object only the destruction of 

 pathogenic microbes. When an object has been ren- 

 dered free from all kinds of micro-organisms and their 

 spores it is said to be sterile, and the process by which 

 sterility is brought about is known as sterilization. 



A deodorant is a substance that has the 



Deodorant, power to destroy a noxious odor, usually 



by substituting its own in place of the 



other. A deodorant may or may not be a disinfectant. 



