314 PATHOGENIC MICROCOCCI 



18. MICROCOCCUS TETRAGENUS. 



First described by Gaffky (Fliigge). Obtained by Koch and 

 Gaffky (1831) from a cavity in the lung in a case of pulmonary 

 phthisis. . Since found occasionally in normal saliva (three times in 

 fifty persons examined by Biondi), and in the pus of acute abscesses 

 (Steinhaus, Park, Vangel). Rather common in the sputum of phthi- 

 sical cases. 



Morphology. Micrococci, having a diameter of about one yu, 

 which divide in two directions, forming tetrads, which are enclosed 

 in a transparent, jelly-like envelope especially well developed as 

 seen in the blood and tissues of inoculated animals. In cultures the 

 cocci are seen in the various stages of division, as large single cells, 



FIG. 98. Micrococcus tetragenus; section of lung of mouse, x 800. (Fliigge.) 



pairs of oval elements, or groups of four resulting from the trans- 

 verse division of these latter. 



Stains quickly with aniline colors, and in preparations from the 

 blood of an inoculated animal the transparent envelope may also be 

 feebly stained. Stains also by Gram's method. 



Biological Characters. This micrococcus grows, rather slowly, 

 in nutrient gelatin at the ordinary room temperature, without lique- 

 faction of the gelatin. Upon gelatin plates small white colonies are 

 developed in from twenty-four to forty-eight hours, which under the 

 microscope, with a low power, are seen to be spherical or lemon- 

 shaped, finely granular, and with a mulberry-like surface. When 

 they come to th6 surface they form white, elevated, and rather thick 

 masses having a diameter of one to two millimetres. In gelatin 

 stick cultures a broad and thick white mass forms upon the surface, 



