748 MICROBIOLOGY OF DISEASES OF MAN AND DOMESTIC ANIMAIS 



monia and the fatalities form about lo 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 wUl 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 

 bacUlary 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 

 for its growth. On agar it grows in small, rather transparent, finely granular 

 colonies, which are larger and more opaque when serum or ascitic fluid is present. 

 Broth is faintly and uniformly clouded. Milk is a favorable medium for most 

 strains and typically is acidified and coagulated. On potato, growth may occur 

 but is invisible. Gelatin can rarely be used at a temperature high enough to allow 

 growth. When occasionally growth is obtained the medium is not liquefied. On 

 blood serum, growth appears as small clear colonies and on the whole is better than on 

 agar. A number of special media are described of which one of the most valuable is 

 the inulin-serum-water medium of Hiss. It typically ferments, with the production 

 of acid, the majority of carbohydrates, even polysaccharides as inulin. On blood 

 agar the typical organism produces a greenish zone in the medium about the growth, 

 but not a clear zone of haemolysis as do niost strains of streptococci. The dif- 

 ferentiation from other streptococci is sometimes a matter of difficulty, and the 

 following characters are of importance — the lanceolate shape, capsule formation, 

 fermentation of inulin, absence of haemolytic powers, agglutination in antipneu- 

 mococcic sera, susceptibility to lysis by the action of bile salts. Acid is an im- 

 portant and characteristic product and, if allowed to accumulate, rapidly kills the 

 organism. The toxic products appear to be closely united with the cell bodies and 

 are only released when these are broken up. The resistance to heat is not great 

 and its thermal death-point is 52°. Light is germicidal if the cocci are not pro- 

 tected in thick masses of sputum. Drjdng is resisted rather well in sputum or the 



