128 BACTERIA 



luxuriantly on any culture media, but are most prolific on one that 

 is faintly acid and contains animal juices like serum. They must be 

 transplanted frequently. On gelatine they grow scantily without 

 liquefaction, the growth consists of discrete little masses, while 

 on agar with glycerine, they appear translucent colonies of very 

 small grayish granula. In bouillon cultures some varieties either 

 cloud the medium uniformly, or else sedimentate in the form of 

 little balls, the supernatant fluid remaining clear. It ferments some 

 simple sugars but does not form gas. In milk the growth is more 

 luxuriant, and becoming acid, is totally coagulated in twenty-four 

 hours. Clotted casein may be digested. On potato the growth 

 is invisible and scanty. 



Vital Resistance. Thermal death-point is 54 C. in five 

 minutes. Virulence in dried albuminous matter (pus) is retained 

 for months. If kept on ice, vitality and virulence are retained 

 for months also. 



Chemical Activities. Lactic acid and sulphuretted hydrogen are 

 produced, also ferments which have the property of dissolving fibrin 

 under anaerobic conditions. They are also capable of dissolving 

 red blood corpuscles, either in culture media or in the body and 

 about cultures on blood agar plates there is a clear halo of hemolysis. 

 They produce a strong soluble toxin, which can be filtered from the 

 bouillon and precipitated with alcohol. This causes necrosis, 

 anaemia and death. 



Habitat. In sewage, dwellings, dust, on the healthy human body, 

 and in the cavities of the respiratory tract, vagina, rectum, and in 

 the feces. It is the cause of many diseases, i.e., erysipelas, puerperal 

 fever, meningitis, pneumonia, endocarditis, peritonitis, tonsillitis, 

 osteomyelitis, and the diarrhoea of children. 



In general septicaemia streptococcus is found in the blood, and 

 plays an important role in secondary infection, causing an aggrava- 

 tion of the original infection, and often death. It is especially active 

 in phthisis, scarlatina, small-pox, and diphtheria, in which diseases 

 it is often the cause of death. Many of the symptoms of phthisis 



