CONTAGIOUS DISEASES 369 



stand how to protect himself and his home, and to cooperate 

 intelligently with the board of health and other organizations 

 whose duty it is to look after the public welfare. 



In considering the part that bacteria play in disease, 

 we need to understand three things : first, how the bacteria 

 leave the body of a sick person ; second, how tliey are dis- 

 tributed from place to place ; and third, how they enter the 

 system of a well person. 



How bacteria leave the body of a sick person. The disease 

 bacteria leave the body in the following ways : in the sputum, 

 in the excreta, in the urine, and in eruptions of the skin. 

 Sometimes patients who have recovered entirely from a 

 contagious disease may continue to give off disease germs 

 from their body for several years, thus proving a source of 

 danger to the community. 



How bacteria are distributed. The chief ways by which these 

 bacteria are distributed are by water, milk, food, flies, and con- 

 tact. By contact is meant the transfer of fresh germs through 

 short distances from patients to people near. This may be 

 through mouth spray, clothing, eating utensils or by direct 

 contact, as in kissing. One of the commonest means of trans- 

 fer by contact is by the hands. These are carried to the mouth 

 many times during the day, and if they have come in contact 

 with moist germs, these germs find easy access to the mouth. 



Formerly it was believed that the germs were carried 

 by dust, books, letters, and other articles that had been 

 touched by the patient ; but to-day modern medicine is 

 emphasizing especially the danger of direct contact with the 

 patient through the hands and the sputum given off as a fine 

 spray in coughing and in conversation. Experiments have 

 shown that in ordinary conversation this spray may be 

 carried three or four feet, and in coughing ten feet. This is 

 believed to be one of the common means by which influenza 

 is carried ; hence the use of cloth masks. 



Since drying and sunlight soon kill bacteria, it is not 



2B 



