NOT DESCRIBED IN SECTIONS V. AND VI. 411 
MICROCOCCUS TETRAGENUS. 
First described by Gaffky (Fligge). Obtained by Koch and 
Gaffky (1881) 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 p, 
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, 
Fia. 96.—Micrococcus tetragenus; section of lung of mouse. x 800. (Fligge.) 
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 the surface they form white, elevated, and rather thick 
masses having a diameter of one to two millimetres. In gelatin 
stab cultures a broad and thick white mass forms upon the surface, 
