MICROORGANISMS AND SANITATION 381 



individual to observe is so to regulate his diet, his exercise, 

 his rest, and his bathing that he may build up a healthy body 

 that will of itself be resistant to disease. He should also take 

 great care to avoid exposure to infection. 



Bacteria or other microbes often gain entrance into the 

 system through impure milk, impure meat, impure water or 

 other impure food. One of the objects in cooking food is 

 to sterilize it thoroughly. Sterilization is the killing of all 

 bacterial life by the application of heat. Bacteria also gain 

 entrance into the system, sometimes, through wounds. For 

 this reason a wound, large or small, should be carefully dis- 

 infected as described on page 327, and should be bound 

 with disinfected or sterilized bandages. Strong acids, alka- 

 lies or other substances that will kill microbes are called 

 disinfectants. 



Quarantine. When a person is ill of an infectious or 

 contagious disease, it is necessary as a matter of safety to 

 other people to place him by himself, allowing no one to 

 enter the room but the nurse and doctor. Thus he is quar- 

 antined. When ships come into harbor from a foreign 

 port, they are placed in quarantine until the health officers 

 have examined the passengers so as to be sure there are no 

 persons on board with contagious diseases. 



Disinfection. After a patient has been ill of an infectious 

 or contagious disease, and before the quarantine has been 

 removed, the room he has occupied, with everything in it, 

 must be made germ-free. This is known as disinfection. 

 The burning of sulphur is an ordinary method of disinfection. 

 The fumes of the burning sulphur kill any harmful bac- 

 teria that may be in the air, in the clothing, or on the walls. 

 There are other disinfectants that are furnished or suggested 

 by Boards of Health. 



Immunity. During an epidemic, that is, when a con- 

 tagious disease as smallpox or diphtheria seems to be spread- 

 ing through a community, it becomes necessary to take ex- 



