152 INFECTIOUS AND PARASITIC DISEASES. 



exits open to the causative agents, and that one disease 

 may, therefore, require greater precautions than another 

 to prevent its spread. In no field of pubHc utihty does 

 knowledge confer greater power than in sanitary 

 science, and in this matter of the exit of micro-organ- 

 isms from the body in disease we have the key to the 

 happiness of families, the prosperity of nations, and to 

 victory in wars. Moreover, it robs disease of its terrors 

 by suggesting protective measures which can be relied 

 upon to be entirely efficient. If all of the infectious 

 agents were efficiently dealt with upon their exit from 

 the body, the various diseases to which they give rise 

 would in time become traditions; but until Arcadia is 

 attained this will not be done. 



Sanitarians in order to work in an enlightened manner 

 must inform themselves of both the direct and indirect 

 sources of disease. A direct source is a diseased person, 

 so that this study begins with the elimination of infec- 

 tious agents from the body. 



In general it may be stated that microbes leave the 

 body in six ways: 



1. In the expectoration and nasal secretion. 



2. In the stools. 



3. In suppurations discharging externally. 



4. From the skin. 



5. In the urine. 



6. From the blood through the bites of suctorial 

 (biting) insects. 



