THE GENERAL PROBLEM OF KEEPING WELL 403 



caused by animal germs. It is also propagated in the 

 same manner as malaria, but by a different variety of 

 mosquito (Stegomyia, Fig. 171). The stamping out of 

 yellow fever in Havana, the Panama Canal Zone, and 

 other places, through the destruction of this variety of 

 mosquito, affords ample proof of the correctness of the 

 " mosquito theory." 



Consumption, or tuberculosis of the lungs, spoken of as 

 the " white plague," was among the first diseases shown 

 to be due to bacteria. Consumption is now recognized as 

 an infectious disease, though not so readily communicated 



FIG. 172. Consumption germs from the spit of one having the disease. 

 Highly magnified and stained. (Huber's Consumption and Civilization.} 



as some other diseases. Several methods are recognized 

 by which the germs are passed from the sick to the well, 

 the most important being as follows : 



1. By personal contact of the sick with the well, espe- 

 cially in kissing. 



2. By the sputum, or spit, which, if allowed to dry, is 

 blown about as dust and breathed into the lungs 1 (Fig. 172). 



3. By means of objects (drinking cups, tableware, etc.) 

 that have been handled by consumptives. 



1 The habit of spitting upon the floors of public buildings and street cars, and 

 also upon sidewalks, is now recognized as a most dangerous practice. Not only 

 consumptives, but people with throat affections, may do no end of harm in the 

 spreading of disease by carelessness in this respect. 



