146 AGEICULTUKAL AND INDUSTKIAL BACTEKIOLOGY 



well known. Some of them are easily destroyed by heat. 

 For example, Bacterium coli when grown upon a culture 

 medium renders that medium unfit for future growth of 

 the same organism until it has been heated. Heating 

 apparently destroys the toxicity of the growth product. 



Use in Therapeutics. Antiseptics or disinfectants 

 which may be used in or upon the human body are, of 

 course, much to be desired. Such substances must have a 

 much higher destructive action upon microorganisms than 

 upon the tissues of the body with which they come in con- 

 tact. Within the past two decades persistent effort has been 

 made to find substances which may be injected into the body 

 to kill certain kinds of microorganisms without injuring the 

 body tissues. Such studies have led to the discovery of sub- 

 stances such as arsphenamine (salvarsan), the so-called 

 specific for syphilis. Certain of the aniline dyes and related 

 chlorine compounds have been found useful in wound dis- 

 infection. 



In a later chapter the ability of the body to produce sub- 

 stances harmful to microorganisms will be discussed. It 

 will be found that in the blood serum substances toxic to 

 bacteria may be developed in sufficient quantities entirely 

 to prevent their growth in the body. 



