438 MICROORGANISMS 



patient. Knowing this, they are able to devise methods of 

 preventing such spread of the disease. 



It is obvious that the first two of these lines of effort must be 

 left to the bacteriologists and physicians but it is quite as 

 obvious that the value of the known methods of preventing the 

 spread of disease depends very largely on the faithful coopera- 

 tion of all the people. Therefore, it is quite important that 

 as nearly as possible, everyone should come to know how the 

 common diseases are ordinarily disseminated and how this 

 dissemination might be prevented. For this reason, this latter 

 phase of disease should be emphasized in a book like this. 



IMPORTANT FACTS ABOUT COMMON DISEASES 



510. Pneumonia. This is primarily a disease of the lungs and 

 is usually caused by a specific spherical bacterium called PNEU- 

 MOCOCCUS. In most serious cases, however, the organism finds 

 its way into the general circulation and is distributed over 

 the body. While pneumococcus is the cause of a majority 

 of the cases of pneumonia, other organisms, such as Bacillus 

 diphtherise, and Bacillus influenzse, and others may cause an 

 inflammation of the lungs which is difficult to distinguish 

 from that resulting from pneumococcus. Often two or more 

 of these organisms are involved in an attack of the disease. 



Pneumococcus and the several other organisms which may 

 cause this disease are very widespread and are very com- 

 monly present in the mouths and throats of healthy persons. 

 As long as the body is in a vigorous state of health, however, 

 it is usually able to ward off an attack but often when weak- 

 ened by other illness, or by exposure to extreme cold, hunger, 

 fatigue, or lack of fresh air or other similar causes, the re- 

 sistance of the body seems to break down and the disease 

 gets a start. This fact explains why the disease so often 

 follows other forms of illness and also why it is more prevalent 

 in the winter time than in the summer. Lack of fresh air in 

 the winter time is a fruitful cause of pneumonia. Hence it is 



