604 NON-PATHOGENIC MICROCOCCI. 



margin, and without lustre. In miflc, at the end of twelve hours, a red 

 color is developed, which disappears at the end of twenty-four hours, when 

 coagulation has occurred as a result of the formation of lactic acid. 



195. MICROCOCCUS LACTIS VISCOSUS. 



Synonym. Micrococcus of bitter milk (Conn). 



Found in cream which had a bitter taste. 



Morphology. Micrococci of moderate dimensions, frequently united in 

 pairs ; in agar cultures forms short chains. 



Biological Characters. Anaerobic and facultative anaerobic, liquefying 

 micrococcus. Grows in the usual culture media at the room temperature 

 more rapidly at 35 C. Upon gelatin plates forms small, spherical colonies, 

 which, as liquefaction commences, spread out upon the surface as a thin, 

 granular mass. In gelatin stick cultures liquefaction commences at the sur- 

 face, forming a shallow cavity, and rapidly progresses until the gelatin is 

 entirely liquefied ; the liquefied gelatin is extremely viscid. Upon agar a 

 shining, homogeneous white layer is developed. Upon potato white, shining 

 masses, which are more or less separated from each other. In bouillon an 

 abundant development occurs and a thin film is formed upon the surface ; 

 the bouillon becomes very viscous. In milk growth is rapid and the milk 

 acquires a bitter taste; at 35 C. coagulation occurs in twenty-four hours and 

 the milk has an acid reaction ; the coagulum is soft and soon commences to 

 dissolve from the peptonizing action of the ferment, but solution is not com- 

 plete. Cultures in gelatin and bouillon are especially viscid, and may be 

 drawn out into threads which are scarcely visible and are as much as three 

 metres long. The acid formed by the growth of this micrococcus in milk is 

 butyric. 



196. SPHJEROCOCCUS ACIDI LACTICI (Marpmann). 



Found in fresh cow's milk. 



Morphology. Very small, oval cocci, in pairs or in short chains. 



Biological Characters. An aerobic, non-liquefying micrococcus. Grows 

 in the usual culture media at the room temperature. Upon gelatin plates 

 forms porcelain-white colonies, the size of a pin's head, upon the surface of 

 the gelatin. In gelatin stick cultures growth is scanty along the line of 

 puncture ; upon the surface a layer is developed which has sloping, toothed 

 margins, and at the end of six weeks acquires a pale-yellow color. Milk ac- 

 quires a reddish color, and is coagulated at the end of twenty-four hours, 

 with formation of lactic acid. 



197. MICROCOCCUS AQUATILIS (Bolton). 



Very common in water. 



Morphology. Small cocci, associated in irregular groups. 



Biological Characters. An aerobic, non-liquefying micrococcus. Grows 

 in the usual culture media at the room temperature. Upon gelatin plates 

 forms circular, porcelain- white, slightly elevated colonies; under a low 

 power the deep colonies are seen to be mulberry-like in form, with roughly 

 toothed contour and a pale-yellowish color; the superficial colonies are cir- 

 cular and are surrounded by a narrow, homogeneous marginal zone, while 

 the interior is peculiarly marked, resembling a schematic drawing of a sec- 

 tion of a liver acinus. In gelatin stick cultures growth occurs both on the 

 surface and along the line of puncture, of a white color. Upon the surface 

 of agar a white layer is formed. 



198. MICROCOCCUS CONCENTRICUS (Zimmermann). 



Found in water. 



Morphology. Micrococci, 0.9 /* in diameter, associated in irregular 

 masses. 



