502 INFECTION AND IMMUNITY. 



pulmonitis: Diplococcus pneumonia, Streptococ- 

 cus pyogenes, Staphylococcus pyo genes, bacillus of 

 Friedlander (B. pneumonia), B. influenza, B. pes- 

 tis, B. diphtheria, B. typhosus, B. coli communis, 

 B. tuberculosis and Micrococcus catarrhaUs. The 

 organisms of tuberculosis, actinomycosis, syphilis 

 and some other infections cause chronic inflamma- 

 tions of the lungs. Some of these organisms have 

 already been considered and others will be dis- 

 cussed later, in their relation to pneumonia, with- 

 out, however, entering into details as to the various 

 types of the disease. The Diplococcus pneumonia 



Pneumonia. / r ^ 



is the commonest cause of lobar pneumonia. It 

 produces lobular pneumonia not infrequently, and 

 has been found as the only organism in acute 

 interstitial pneumonia (Weichselbaum). 



Friedlander (1882) found that capsulated cocci 

 were present constantly in the exudate of pneumo- 

 nia. Such cocci in all probability represented the 

 organism which at present is known as the pneu- 

 mococcus, yet the cultures which he obtained some- 

 what later showed the characteristics of the organ- 

 ism now known as the bacillus of Friedlander. 

 Fraenkel, in 1884, obtained the first-named coccus 

 in pure culture, and his investigations, together 

 with those of Weichselbaum and many others, 

 eventually established the independence of the 

 two organisms. 

 Typical and The typical pneumococcus is slightly elongated, 



Non-Typical , , , r . ,*f ,. -, ij. 5- 'I 



strains, and both in the tissues and in culture media it 

 grows in pairs. Typically, also, the pair possesses 

 a capsule which is present constantly in the tissues 

 and may be obtained on certain culture media 

 (milk and serum). It is non-motile, non-flagel- 

 lated, forms no spores and stains by Gram's method. 



