DIPLOCOCCUS LANCEOLATUS. 183 



the entire stab. They remain distinctly separate. Its lim- 

 ited growth is apparent even in the most suitable medium. 

 On agar-agar and blood-serum the growth is often overlooked, 

 the colonies are so very small and transparent. Bouillon is 

 slightly clouded. Agar-agar may be covered with a thin 

 film of blood-serum and used for a culture-medium. When 

 desirable to increase the virulence of the germ, it must be 

 passed through animals. 



The development of the diplococcus is checked by a 1 : 400 

 solution of boric acid ; 1 : 20,000 mercuric chloride solution 

 or a 1 per cent, solution of carbolic acid destroys its vitality 

 in two hours. In the dry state it retains its virulence for a 

 long time. This is of importance when considering the 

 methods of infection. 



Pathogenesis : The pneumococcus is always found in the 

 rusty sputum of lobar pneumonia, and is usually associated 

 with other germs, especially the streptococcus and staphylo- 

 coccus. It has also been found in meningitis, sore throat, 

 endocarditis, otitis media, acute abscess, and in the sequelae 

 of croupous pneumonia. The bloodvessels and the lymph- 

 atics, especially the latter, carry the germ to other parts of 

 the body from the original site of infection. 



Infection usually occurs through the respiratory tract, 

 although in secondary pneumonia the pneumococcus may find 

 its way to the lung through the bloodvessels. But this 

 method of infection is extremely infrequent. The air con- 

 veys the germ from place to place, and thus gives rise to 

 epidemics of pneumonia. In order to prevent this dissemina- 

 tion it is absolutely necessary to prevent desiccation of the 

 germ, and this can only be done by receiving the sputum in 

 a proper receptacle containing an antiseptic solution. This 

 solution not only prevents drying, but it also kills the germ. 

 A 2 per cent, carbolic acid solution answers the purpose 

 admirably. Neglect of these precautions is undoubtedly 

 responsible for the so-called house epidemics of pneumonia, 

 several instances of which have been recorded. 



In view of the fact that the pneumococcus may be found 

 in the mouths of healthy individuals, it is evident that condi- 

 tions predisposing to infection must exist before the disease 



