MICROBIAL DISEASES OF MAN AND DOMESTIC ANIMALS 745 



cases, death may occur without any apparent compUcation, or it may 

 follow meningitis, pericarditis, nephritis, or some other sequel. In sim- 

 ple uncomplicated fatal cases the liver, kidneys and spleen are swollen 

 and soft and show degenerative changes in the gland cells. 



Pasteur, Koch, Rosenbach and Fehleisen divide the earlier honors in 

 the gradual working out of the relationships of streptococci to disease. 



Blood culture in plain broth in the case of septicaemia or inoculation 

 of plain nutrient agar from pus are practically always successful. 

 Growth is never luxuriant on the ordinary media. Cultivation from 

 cases of erysipelas is less easy because most of the organisms are found 

 at the margin of the lesion and are difficult to reach. 



In exudates a stained smear will usually demonstrate the chain- 

 forming coccus at once. 



The cocci vary in size from 0.41J1 to iju. In shape the organisms may be rounded 

 or oval or with one aspect flattened when occurring in pairs. The chains may be long 

 or short and a grouping into pairs is frequent even within the chain. There are no 

 true spores developed and the organism is non- motile. Capsules are not found on 

 the majority of streptococci. Staining the organism is easily accomplished with the 

 ordinary aniline dyes. It is Gram-positive. The temperature range in which 

 streptococci are capable of growing is about from 15° to 45°, the optimum tem- 

 perature is about 37°. Streptococci are, as a rul6, aerobes and facultative anaerobes 

 Strict anaerobic species are said to have been isolated from faeces. The reaction of 

 media should be slightly alkaline. Acid production is a striking feature of this 

 organism and has a decided inhibitive effect upon its growth. Concerning the 

 action on carbohydrates this organism typically forms acid from monosaccharides, 

 lactose, saccharose, and salicin. Gas is never produced. Nitrates are reduced by 

 some streptococci to nitrites. The production of hydrogen sulphide is characteristic 

 of some forms which have been grouped as Strept. fcecalis. No pigment is found 

 other than the slight brownish tinge seen in some gelatin cultures. Typically 

 actively hEemolytic. This power may be lost on cultivation. The toxic products 

 of the streptococci have been the subject of a great deal of investigation, but few 

 definite facts have been discovered. When cultivated on plain nutrient agar the 

 growth is visible in eighteen to twenty-four hours as small round translucent finely 

 granular colonies, which possess an even or notched border, and a tendency to remain 

 discrete except when thickly sown. The center is thickened and the margins thinner. 

 In plain nutrient broth the majority of long-chained varieties produce at the bottom 

 and along the sides of the tube a granular deposit, or small flocculi or large flakes, 

 leaving the remainder of the broth clear. A few long-chained varieties cloud the 

 broth uniformly. The short-chained streptococci, as a rule, produce a cloudiness in 

 the medium which remains for a number of days even though a finely granular 

 deposit accumulates at the bottom of the tube. On plates of plain nutrient gelatin 

 the colony formation remains the same as that on agar. In stab cultures a finely 



