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MICROCOCCUS TETRAGENUS. 

 Koch, Gaffky (1881). 



Origin. First obtained from the contents of a tuber- 

 cular lung cavity; present in normal saliva (26-times out 

 of 111 cases, MILLER), rather common in sputum of tuber- 

 cular persons. Has been found in a few instances, as the 

 only organism present in acute abscesses. 



Form. Large cocci, which in pure cultures on artifi- 

 cial media are either single or in pairs, or irregular groups. 

 In the animal body it forms perfect tetrads, which are 

 surrounded by a wide colorless capsule. 



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, 



Stich Cultures. Along the line of inoculation, in the gelatin tube, the 

 growth develops either as a row of white dots or as a continuous white line. 

 On the surface a characteristic moist, white, thick mass forms. 



Streak Cultures. On agar usually develops as sharply defined, round, 

 white colonies. On potatoes it forms a thick, slimy covering, which can be 

 drawn out into long threads. 



Oxygen requirements. Is aerobic, and also fac- 

 ultative anaerobic. 



Temperature. Grows well at ordinary temperature ; 

 better in the incubator. 



Behavior to Gelatin. Does not liquefy. 



Attenuation. Cultures grown for years on artificial 

 media eventually become attenuated. 



Pathogenesis. White mice and guinea-pigs are 

 susceptible. House and field mice are usually insuscepti- 

 ble, while rabbits are immune. By subcutaneous applica- 

 tion or intraperitoneal injection, white mice and guinea- 

 pigs die in from 3-10 days. The blood-vessels of the kid- 

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

 invested by capsules. 



