Micrococcus Tetragenus 363 



Agar-agar. Upon agar-agar spheric white colonies are 

 produced. They may remain discrete or become confluent. 



Potato. Upon potato a luxuriant, thick, white growth 

 is formed. 



Blood-serum. The growth upon blood-serum is also 

 abundant, especially at the temperature of the incubator. 

 It has no distinctive peculiarities. 



Pathogenesis. The introduction of tuberculous sputum 

 or of a minute quantity of a pure culture of this coccus into 

 white mice usually causes a fatal bacteremia in which these 



Fig. 109. Micrococcus tetragenus; colony twenty-four hours old upon 

 the surface of an agar-agar plate. X 100 (Heim). 



organisms are found in small numbers in the heart's blood, 

 but are numerous in the spleen, lungs, liver, and kidneys. 



Japanese mice and white mice are highly susceptible to the 

 organism and die three or four days after inoculation. 



House-mice, field-mice, and rabbits are comparatively 

 immune. Guinea-pigs may die of general septic infection, 

 though local abscesses result from subcutaneous inoculation. 



The tetracocci, when present, probably hasten the tissue- 

 necrosis in tuberculous cavities, aid in the formation of ab- 

 scesses of the lung, and contribute to the production of the 

 hectic fever. 



An interesting contribution to the relationship of this 

 coccus to human pathology has been made by Lartigau,* 

 who succeeded in demonstrating that the tetracoccus may 



* << Phila. Med. Jour.," April 22, 1899. 



