320 Suppuration 



spheric or elongate (lemon shaped), finely granular, and lobulated 

 like a raspberry or mulberry. When superficial they are white and 

 elevated, i to 2 mm. in diameter. 



Gelatin. In gelatin punctures a large white surface growth 

 takes place, but development in the puncture is very scant, the 

 small spheric colonies usually remaining isolated. The gelatin is 

 not liquefied. 



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. 



Fig. 113. Micrococcus tetragenus; colony twenty-four hours old upon the 

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



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 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 ab- 

 scesses result from subcutaneous inoculation. 



The tetracocci, when present, probably hasten the tissue-necrosis 

 in tuberculous cavities, aid in the formation of abscesses 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 be the cause of a pseudo- 

 membranous aijgina, 3 cases of which came under his observation. 

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



