When disease germs are within the body, the problem is far from simple, because chemicals which would effectively destroy the germs would be fatal to life itself.  But when germs are outside the body, as in water or milk, or on clothing, dishes, or furniture, they can be easily killed.  One of the best methods of destroying germs is to subject them to intense heat.  Contaminated water is made safe by boiling for a few minutes, because the strong heat destroys the disease-producing germs.  Scalded or Pasteurized milk saves the lives of scores of babies, because the germs of summer complaint which lurk in poor milk are killed and rendered harmless in the process of scalding.  Dishes used by consumptives, and persons suffering from contagious diseases, can be made harmless by thorough washing in thick suds of almost boiling water.

The bedding and clothing of persons suffering with diphtheria, tuberculosis, and other germ diseases should always be boiled and hung to dry in the bright sunlight.  Heat and sunshine are two of the best disinfectants.

232.  Chemicals.  Objects, such as furniture, which cannot be boiled, are disinfected by the use of any one of several chemicals, such as sulphur, carbolic acid, chloride of lime, corrosive sublimate, etc.

One of the simplest methods of disinfecting consists in burning sulphur in a room whose doors, windows, and keyholes have been closed, so that the burning fumes cannot escape, but remain in the room long enough to destroy disease germs.  This is probably the most common means of fumigation.

For general purposes, carbolic acid is one of the very best disinfectants, but must be used with caution, as it is a deadly poison except when very dilute.

Chloride of lime when exposed to the air and moisture slowly gives off chlorine, and can be used as a disinfectant because the gas thus set free attacks germs and destroys them.  For this reason chloride of lime is an excellent disinfectant of drainpipes.  Certain bowel troubles, such as diarrhoea, are due to microbes, and if the waste matter of a person suffering from this or similar diseases is allowed passage through the drainage system, much damage may be done.  But a small amount of chloride of lime in the closet bowl will insure disinfection.

233.  Personal Disinfection.  The hands may gather germs from any substances or objects with which they come in contact; hence the hands should be washed with soap and water, and especially before eating.  Physicians who perform operations wash not only their hands, but their instruments, sterilizing 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.