MICROBIAL DISEASES OF MAN AND ANIMALS. 597 



DiplococcMs penumonia, or Pneiimococcus. As occasional causes of pneu- 

 monia should be mentioned Streptococcus pyogenes, Staphylococcus pyog- 

 enes var. aureus, B. coli, Bact. diphtheria, Bact. influenza;, B. capsulatus 

 mncosus (pneumobacillus), B. typhosus and Bact. tubercnlosis. 



Pneumonia is world-wide in its distribution and is estimated to 

 form anywhere from i to 7 per cent of all cases studied in internal medicine. 

 It appears to be more frequent in regions subjected to sudden changes 

 of temperature. 



The incubation period is two or three days of rather indefinite prodro- 

 mata. 



The onset of the disease is marked by a chill, pain in the side, and rise 

 in temperature. The respirations become frequent. The fever as a rule 

 runs between 102 and 105 F. for from five to ten days and then in 

 favorable cases terminates by a sudden drop of temperature to normal 

 within a few hours (crisis) . 



The most striking pathological findings are a marked congestion and 

 oedema of the lungs following which the lung becomes solid, airless and 

 of a dark red color, the alveoli showing, microscopically, a fibrinous 

 exudate with large numbers of red blood cells, some leucocytes and 

 desquamated epithelium. Thereafter the lung becomes slightly softer 

 and is of a gray color, while microscopically the red cells degenerate 

 and leucocytes are more and more evident. The final stage, resolution, 

 is marked by the liquefaction and absorption of the contents of the 

 alveoli and the entrance of air. 



Death occurs from toxaemia or complications such as carditis, menin- 

 gitis, etc. Roughly about 10 per cent of all deaths are due to pneumonia 

 and the fatalities form about 10 per cent of the total number of cases. 



The Streptococcus pneumonia was described, as found in the sputum, 

 by C. Frankel in 1884. 



A Gram-stained preparation of the sputum is sufficient to detect the diplococci but 

 cultures are necessary for positive indentification. Some medium richer than the ordi- 

 nary by the addition of blood or serum from man or animals is best, and may be inocula- 

 ted from the blood and organs or from sputum and other contaminated sources by streak- 

 ing or plating. Injection of sputum into white mice or rabbits will often cause a fatal 

 septicaemia in these animals and the coccus may then be obtained in pure culture from 

 the heart's blood. Occurs as pairs of oval or lanceolate cocci, with their contiguous 

 surfaces somewhat flattened and the distal ends slightly pointed. From this type the 

 organism may vary to spherical or short bacillary forms. It may occur also singly or in 

 chains of varying length usually consisting of not more than about six or eight individ- 



