MICROCOCCUS TETRAGENUS. 171 



color. Milk is coagulated. Bouillon becomes clouded and is 

 colored green. 



Pathogenesis : In man the organism appears to be purely 

 saprophytic, whereas in animals it is intensely pathogenic, 

 especially when injected into the subcutaneous tissues. It 

 has been found in otitis media, pulmonary tuberculosis, peri- 

 carditis with effusion, acute angina, meningitis, bronchopneu- 

 monia, dysentery, diarrhoea, etc. 



Micrococcus Tetragenus. 



This germ belongs to the same class as Bacillus pyocyaneus. 

 It is usually found in tubercular septicaemia in association 

 with other bacteria, in the pus of empyema subsequent to 

 pneumonia, and occasionally in the saliva of healthy persons. 



Biology and morphology : In the tissues this organism occurs 

 in squares of four cocci (Fig. 72). It is not motile ; does 



Tetracoccus. (Park.) 



not sporulate ; has no flagella ; and stains readily with Gram's 

 and the anilin dyes. It grows well on all the various nutrient 

 media at either room or body temperature. It is a faculta- 

 tive aerobe. It measures about 1 p. in diameter, and is fre- 

 quently surrounded by a gelatinous capsule. 



In blood cultures it produces minute white colonies with a 

 somewhat opalescent appearance. They are very finely granu- 



