252 CHEMICAL DISINFECTANTS AND PRESERVATIVES 



and especially before eating. Physicians who perform opera- 

 tions wash not only their hands, but their instruments, steril- 

 izing the latter by placing them in boiling water for several 

 minutes. 



Cuts and wounds allow easy access to the body ; a small 

 cut has been known to cause death 'because of the bacteria 

 which found their way into the open wound and produced 

 disease. In order to destroy any germs which may have 

 entered into the cut from the instrument, it is well to wash out 

 the wound with some mild disinfectant, such as very dilute 

 carbolic acid or hydrogen peroxide, and then to bind the 

 wound with a clean cloth, to prevent later entrance of germs. 



234. Chemicals as Food Preservatives. The spoiling of 

 meats and soups, and the souring of milk and preserves, are 

 due to germs which, like those producing disease, can be 

 destroyed by heat and by chemicals. 



Milk heated to the boiling point does not sour readily, and 

 successful canning consists in cooking fruits and vegetables 

 until all the germs are killed, and then sealing the cans so 

 that germs from outside cannot find entrance and undo the 

 work of the canner. 



Some dealers and manufacturers have learned that certain 

 chemicals will act as food preservatives, and hence they have 

 replaced the safe method of careful canning by the quicker 

 and simpler plan of adding chemicals to food. Catchup, 

 sauces, and jellies are now frequently preserved in this way. 

 But the chemicals which destroy bacteria frequently injure 

 the consumer as well. And so much harm has been done 

 by food preservatives that the pure food laws require that 

 cans and bottles contain a labeled statement of the kind 

 and quantity of chemicals used. 



Even milk is not exempt, but is doctored to prevent sour- 

 ing, the preservative most generally used by milk dealers 



