CHAPTER XL. 

 THE PNEUMOCOCCUS. 



Synonyms : Streptococcus lanceolatus : Micrococcvs pasteuri. 



Introduction. 



Section I. Experimental inoculation, p. 581. 



Section II. Morphology, p. 582. 



1. Microscopical appearance and staining reactions, p. 582. 2. Cultural charac- 

 teristics, p. 584. 



Section III. Biological properties, p. 585. 



1. Vitality and virulence, p. 585. 2. Bio-chemical reactions, p. 586. 3. Toxins, 

 p. 586. 4. Vaccination, p. 587. 5. Serum therapy, p. 588. 6. Agglutination, 

 p. 589. 7. Precipitins, p. 590. 8. Immune body, p. 590. 



Section IV. Detection., isolation and identification of the pneumococcus, p. 590. 



THE pneumococcus is the infecting agent in acute lobar pneumonia (Talamon, 

 Frankel), but this does not represent the limit of its setiological role for it is 

 concerned in by far the greater number of the complications of pneumonia, 

 as well as in certain other affections. 



(i) The pneumococcus is frequently found in the saliva of healthy persons (Pasteur 

 and others). Netter found it in the saliva of persons who had recently recovered 

 from an attack of pneumonia in four out of five cases examined, and once out of five 

 cases examined in that of persons who had never suffered from the disease. He 

 showed that during the early stages of the disease the pneumococcus in the saliva of 

 the persons included in the former series was virulent, that it disappeared at the 

 time of the crisis, and reappeared at the end of a fortnight. The pneumococcus 

 is an habitual inhabitant of the tonsillar mucus (Bezan9on and Griffon), and Burger 

 isolated it from the mouths of many healthy persons (34 out of 100 examined). In 

 the latter it lives as a harmless parasite in the mouth : but should the resistance of 

 the tissues from any cause become lowered, the organism overcomes the leucocytic 

 defences and invades the lung. 



(ii) In lobar pneumonia, the pneumococcus is always found in the area of hepatiza- 

 tion where it may be present in pure culture or be associated with other micro- 

 organisms, generally streptococci, staphylococci and the bacillus of Friedlander : 

 it occurs also in the characteristic rusty sputum. Some cases of broncho-pneumonia 

 are due to the pneumococcus. 



(iii) The pneumococcus occasionally passes into the blood- stream and gives rise 

 to complications, often of the nature of a suppuration, in the neighbourhood of the 

 lung or in more distant parts (Friedlander, Talamon, Frankel). Pneumococcal pus 

 is thick and viscous, very rich in cellular elements and greenish in colour. Sup- 

 puration due to the pneumococcus tends to undergo spontaneous resolution. 



(iv) Pleurisy, pericarditis fibrinous or purulent, endocarditis vegetative or 

 ulcerative, meningitis, nephritis, suppurative parotitis, suppurative arthritis, 

 peritonitis, metritis and abscesses, as complications of pneumonia may any or all 



