582 Tetragenus 



lar arrangement in tetrads as constantly as in the blood and 

 tissues of animals where they occur in groups of four sur- 

 rounded by a transparent gelatinous capsule. 



Staining. The organisms stain well by ordinary methods, 

 and beautifully by Gram's method, by which they can be 

 best demonstrated in tissues. 



Isolation. The organism can be isolated by inoculating 

 a white mouse with sputum or pus containing it. After 

 death it can be recovered from the blood. 



Cultivation. It grows readily upon artificial media. 

 Upon gelatin plates small white colonies are produced in 

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

 scope they appear spheric or elongate (lemon-shaped), finely 



Fig. 168. Micrococcus tetragenus; colony twenty-four hours old upon 

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



granular, and lobulated like a raspberry or mulberry. When 

 superficial they are white and elevated, 1-2 mm. in diameter 

 (Fig. 1 68). 



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 



