TETRAGENUS. 323 



most beautifully by Gram's method, by which it can be 

 best demonstrated in tissues. 



Upon gelatin plates small white colonies are produced 

 in from twenty-four to forty-eight hours. Under the 

 microscope they are found to be spherical or elongate 

 (lemon-shaped), finely granular, and lobulated like a 

 raspberry or a mulberry. When superficial they form 

 white, elevated, rather thick masses 1-2 mm. in diameter 

 (Fig. 104). 



In gelatin punctures a large white surface-growth 



.x. 



w 



FIG. 104. Micrococcus tetragenus: colony twenty-four hours old upon the sur- 

 face of an agar-agar plate; x 100 (Heim). 



takes place, but very scant development occurs in the 

 puncture, where the small spherical colonies generally 

 remain isolated. 



Upon the surface of agar-agar spherical white colonies 

 are produced. They may remain isolated or may become 

 confluent. 



Upon potato a luxuriant thick, white growth occurs. 



The growth upon blood-serum is also abundant, espe- 

 cially at the temperature of the incubator. It has no 

 distinctive peculiarities. 



The introduction of tuberculous sputum or of a most 

 minute quantity of a pure culture of this coccus into 

 white mice generally causes a fatal septicemia. 



