264 THE PYOGENIC COCCI 



tincture of iodin or iodoform. Sterilization is usually accomplished 

 within ten minutes after the iodin is applied. 



Staphylococcus Pyogenes Citreus. This organism differs from 

 Staphylococcus aureus chiefly in the color of the pigment it produces, 

 a lemon yellow, and a lessened ability to liquefy gelatin. 



Staphylococcus Pyogenes Albus. In many instances this organism 

 is an achromogenic variant of Staphylococcus aureus: it produces 

 white colonies on agar and gelatin, it liquefies gelatin slowly, and it 

 is somewhat less pathogenic for rabbits; many strains do not ferment 

 mannite. 



Staphylococcus Epidermidis Albus. Welch first described this 

 organism, which appears to be a degenerate Staphylococcus albus; 

 it does not liquefy gelatin and its pathogenic powers are practically 

 nil. It frequently causes the troublesome but relatively benign 



stitch abscesses." It appears to be a very constant parasite on the 

 skin. 



Micrococcus Tetragenus. Micrococcus tetragenus was first de- 

 scribed by Gaffky; 1 he found it in cavities of the lung in pulmonary 

 tuberculosis. It occurs but rarely in pure culture in abscesses either 

 in man or animals, 2 but it is often present in the saliva; occasionally 

 it has been recovered from dento-alveolar abscesses. 3 



Morphology. The organism occurs typically in tetrads, enclosed in 

 transparent gelatinous capsules which require special staining methods 

 for their demonstration. The individual cells are about 1 micron in 

 diameter. In artificial media the tetrad arrangement may disappear 

 and the cocci occur chiefly in pairs and groups of three or four pairs. 

 The tetrad arrangement and the capsule are restored by passage 

 through animals. The organism is non-motile, and possesses no fla- 

 gella. It forms no spores and stains readily with ordinary anilin dyes. 

 It is Gram-positive. 



Isolation and Culture. Micrococcus tetragenus grows rather slowly 

 in all ordinary media, particularly the first transfers from the tissues 

 to artificial media. It can be isolated readily in pure culture in gelatin 

 or agar plates; the colonies are small, round and grayish, 0.5 to 0.75 

 mm. in diameter. 



Growth in Media. The organism does not liquefy gelatin, casein, 

 or blood serum. Acid is produced in dextrose, lactose, saccharose, and 



1 Mitt. a. d. kais. Gesamte, i, p. 1. 



2 Miiller, Wien. klin. Wchnschr., 1904, xvii, 1815. 



3 Goadby, Mycology of the Mouth, 1903, p. 101. 



