Micrococcus Tetragenus, Gaffky (1881). 



Origin. — First obtained from the contents of a tubercular lung' 

 cavity; present in normal saliva (26 times out of 111 cases, Miller), 

 rather common in sputum of tubercular persons. Has been found in 

 ■a few instances, as the only organism present in acute abscesses. A 

 similar non-pathogenic organism which, however, cannot be grown 

 artificially, may be present in the mouth. 



Form. — Large cocci, which in pure cultures on artificial media " 

 are either single or in pairs, or in irregular groups. In the animal body 

 it forms perfect tetrads, which are surrounded by a wide colorless 

 capsule (Pig. 5 6, p. 29). 



Motility. — None. 



Sporulation. — None. 



Anilin dyes. — Stain readily. Gram's method is applicable. 



Growth. — Is rather slow. 



Plates. — The colonies which develop on the gelatin plate are round or oval, slightly 

 granular, yellowish and sharp bordered. No liquefaction. The surface colonies are white, 

 elevated and thick. 



Stab culture. — Along the line of inoculation, in the gelatin tube, the growth develoiis 

 either as a row of white dots or as a continuous white line. On the surface a characteristic 

 moist, white, thick mass forms. 



Streak culture. — On agar it usually develops as discrete sharply defined, round, white 

 colonies. At times the growth may be confluent. On potato it forms a thick, slimy cover- 

 ing, which can be drawn out into long threads. 



Oxygen requirements. — It is a facultative anaerobe. 



Temperature. — Grows well at ordinary temperature; better in 

 the incubator 



Behavior to gelatin. — Does not liquefy. 



Attenuation. — Cultures grown for yeaiJs on artificial media even- 

 tually become attenuated. 



Pathogenesis. — White mice and guinea-pigs are susceptible. 

 House and field mice are usually insusceptible, while rabbits and dogs 

 are immune. A subcutaneous application or intraperitoneal injec- 

 tion kills white mice in from 3-10 days. The blood-vessels of the kid- 

 ney, spleen, liver, lungs, etc., are full of the tetrads which are in- 

 vested by capsules. Subcutaneous injection into guinea-pigs pro- 

 duces usually a local abscess; whereas an intraperitoneal injection is 

 followed by a purulent peritonitis. The exudate in this case is rich 

 in capsulated forms. The frequent presence of this organism in 

 tuberculous cavities indicates that it plays, as well as streptococci 

 and other bacteria, an active part in the destruction of the lung 



tissue. 



370 



