MICROBIAL DISEASES OF MAN AND DOMESTIC ANIMALS 799 



The incubation period is two or three days of rather indefinite 

 prodromata. 



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 io5F. 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 degener- 

 ate and leucocytes are much more in evidence. The final stage, resolu- 

 tion, 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, men- 

 ingitis, etc. Roughly about 10 per cent of all deaths are due to pneu- 

 monia and the fatalities form about 10 per cent of the total number of 

 cases. 



The Streptococcus pneumonia was described, as found in the spu- 

 tum, by C. Frankel in 1884. 



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

 but cultures are necessary for positive identification. Some medium richer than 

 the ordinary by the addition of blood or serum from man or animals is best, and 

 may be inoculated from the blood and organs or from sputum and other contami- 

 nated sources by streaking 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. It 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 individuals. Well developed capsules 

 which may surround the single organism or the pairs and chains may be found in 

 exudates or in milk and serum media. There are no spores nor flagella. The 

 cocci stain readily with the aniline dyes and are Gram-positive. The capsule can 

 be demonstrated by several methods of which Welch's and Hiss' are the most 

 common. The temperature range is from 25 to 41. It is both aerobic and 

 anaerobic, and grows most readily in a medium slightly alkaline to phenolphthalein. 

 Besides serum or blood, glycerin, nutrose and dextrose are found to be favorable 



