48 BACTERIOLOGY. 



orchitis, and the vaginitis of children. Serum ob- 

 tained from animals that have been immunized with 

 living cultures of gonococci (active immunization) 

 has also been only partly successful, probably because 

 there seems to be a great many different strains or 

 families of gonococci. 

 The pneu- Pneumonia is an acute infectious disease caused 



mococcus . . . 



by a variety of micro-organisms, the chief one being 

 the Diplococcus pneumonia, or the pneumococcus. 

 Other bacteria, such as the streptococcus, staphylo- 

 coccus, the influenza and typhoid bacillus, may also 

 cause pneumonia. 



The pneumococcus is a small, lance-shaped organ- 



ism, usually arranged in pairs, and these pairs may 

 form chains not unlike the streptococcus in appear- 

 ance. About each pair there may be seen in suitable 

 preparations a capsule with a clear zone between it 

 and the body of the organism. The capsule is seen 

 best in smears of the fresh sputum from pneumonia 

 patients, and is of considerable importance in identify- 

 ing the organism. 



Pneumococci are present in the mouth and throat 

 of most persons in health, and cause no injury or 

 infection unless the resistance of the individual is 

 lowered. Some of the factors that lower the re- 

 sistance are: exposure, alcoholism, debilitating and 

 wasting diseases, unhealthy surroundings, and other 

 infectious diseases, particularly scarlet fever and 

 measles. When the resistance has been lowered the 

 pneumococci in the mouth or throat may gain en- 



