MICROCOCCUS. 163 



Saro. rosea. On tlie contrary, the culture we obtained from Knil, upon 

 agar, hay decoction, and urine, contained bales of packets. 



3. Micrococcus (Cohn). 



The cells divide irregularly in various directions and lie 

 singly, in pairs, in fours, or, finally and indeed mostly, in 

 irregularly bunched heaps. In this class are included all 

 cocci which are not undoubted streptococci or sarcinas. 



Key to the Determination of the Micrococci. 



I. Does not grow upon any of the ordinary nutrient media aerobic- 

 ally or anaerobiciilly ; on the contrary, grows upon human hlood- 

 serum, agar smeared with blood, etc. Microscopically, pairs of kidney- 

 shaped cocci, connected by a usually broad, unstained cement line ; 

 round forms are more rare. Does not stain bij Gram's method. Never 

 found except in human body or its secretions. Micr. gonorrhceae 

 Neisser, page 164. 



II. Poor growth upon the ordinary nutrient media and upon serum. 

 Besides cocci, often rod-forms ( !) are found, which may be four times 

 as long as wide ; not stained by Gram's method. Micr. melitensis 

 Bruce, page 168. 



III. Upon the ordinary nutrient media a thick, white, abundant 

 growth, sometimes forming tetrads. In animal body always tetrads 

 with marked gelatinous capsules. Micr. tetragenus Gaflky, page 171. 



IV. Grow upon ordinary nutrient media ; always spherical ; no 

 tetrads in animal body. 



A. Upon gelatin and agar, do not produce pigments [white to gray 

 varieties) . 



(a) Gelatin not liquefied ; colonies in plate roundish with no out- 

 growths. 



(a) Growth on gelatin and agar thick, pure white ; not patho- 

 genic ; arrangement irrregular. 



1. Individuals ratber large. Micr. candicans Fliigge, page 

 169. . 



2. Individuals very small. Micr. aquatilis Mead Bolton, page 

 171. 



(/3) Similar to (J, but color yellowish-gray, not pure white. Micr. 



rosettaceus Zimmermann. 

 (y) Growth upon gelatin thin and iridescent. Micr.concentricus 

 Zimmermann, page 174. 

 (6) Gelatin not liquefied ; delicate white tendrils extend outward 

 from the deep colonies in gelatin plates and from the gelatin stab. 

 Micr. viticulosus Katz, page 174. 



(e) Gelatin liquefied ; plate and stab cultures without tendrils or 

 branches. Micr. pyogenes y albus (Eosenbach), L. and N. ,' page 187. 



^ Compare Micr. Freudenreichii Guillebeau, Micr. acidi lactis 

 Kriiger. 



