364 EXPERIMENTS WITH PLANTS 



Bacteria in general grow best at from 80 to 95 F. 

 Below 40 F. and above 110 F. they make practically 

 no growth. The temperature of ice fails to kill many 

 kinds; even that of liquid air (minus 310 F.) does not 

 kill all kinds. 



Bright light kills many kinds, while others are not 

 much affected by it. 



Formalin is a good example of a disinfectant which 

 kills the bacteria. (Disinfectants which kill the germs 

 are called germicides, those which thoroughly check 

 their growth or stop it are called antiseptics.) One part 

 in 5,000 or 10,000 of water is said to be efficacious 

 against many bacteria; articles may be disinfected by 

 leaving them for a few hours in a closed box exposed 

 to formalin vapor, or sulphur may be burned in any 

 closed space with good results. Other chemical dis- 

 infectants are chloride of lime, corrosive sublimate, 

 carbolic acid, potassium permanganate, strong mineral 

 acids, etc. 1 



The effect of sterilization is due to the fact that bac- 

 teria in their ordinary or vegetative condition are killed 

 by the heat of steam. Some of the bacteria found in 



1 The following will serve to indicate approximately the strength to be 

 used : Carbolic acid 3 per cent or one tablespoonful of the ordinary solu- 

 tion to a pint of water; lysol 1 to 2 per cent; copper sulphate 1 to 2 per cent; 

 chloride of lime 3 per cent; potassium permanganate 1 to 2 per cent (useful 

 as deodorizer also); corrosive sublimate one-tenth of 1 per cent; hydrogen 

 peroxide nearly full strength; listerine full strength. Wounds should be well 

 washed with disinfectant solution by means of a pipette and then covered with 

 iodoform, or powdered boracic acid. 



