CHAPTER XII. 

 TETRAGENUS. 



THERE can sometimes be found in the normal saliva, 

 more commonly in tuberculous sputum, and still more 

 commonly in the cavities of tuberculosis pulmonalis, a 

 large micrococcus grouped in fours and known as the 

 Micrococcus tetragenus (Fig. 123). It was discovered by 



FIG. 123. Micrococcus tetragenus in pus from a white mouse; x 615 (Heim). 



Gaffky, and subsequently carefully studied by Koch and 

 Gaffky. It sometimes occurs in the pus of acute ab- 

 scesses, and may be of importance in connection with 

 the pulmonary abscesses which so often complicate tu- 

 berculosis. 



The cocci are rather large, measuring about i // in 

 diameter. In cultures they show no particular arrange- 

 ment among themselves, but in the blood and tissues of 

 animals they commonly appear arranged in groups of 

 four surrounded by a transparent gelatinous capsule. 



The organfem stains well by ordinary methods, and 



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