NON-PATHOGENIC MICROCOCCI. 



609 



Stains with the aniline colors usually employed and by Gram's method. 



Biological Characters. An aerobic, liquefying staphylococcus. Grows 

 in the usual culture media at the room temperature. Is killed by exposure 

 to a temperature of 60 C. for ten minutes. Vitality not destroyed by long 

 exposure to a freezing temperature. Development occurs at a comparatively 

 low temperature 10 to 15 C. Preserves its vitality for several months in 

 cultures. In gelatin stick cultures development occurs along the line of 

 puncture and liquefaction in cup shape near the surface ; the cocci accumu- 

 late at the bottom of the cup as a milk-white deposit; later the gelatin may 

 be completely liquefied at the upper part of the tube for half an inch or 

 more, and the non -liquefied gelatin forms a horizontal floor upon which a 

 milk-white deposit is seen. In agar stick cultures an irregular, white, opaque 

 growth is seen along the line of puncture, and a soft, milk-white layer, 

 with irregular outlines, forms upon the surface. Upon potato a milk-white 

 layer, from three to five millimetres wide, is developed along the line of in- 

 oculation at the end of forty-eight hours at 37 C. Does not coagulate milk. 



FIG. 199. FIG. 200. 



FIG. 199. Micrococcus of Freire, from a gelatin culture, x 1,000. From a photomicrograph. 

 (Sternberg.) 



Fm. 200. Culture of Freire's micrococcus in nutrient gelatin, end of eight dayg at 28 C. From 

 a photograph. (Sternberg.) 



In the writer's experiments this micrococcus has not proved to be patho- 

 genic for guinea-pigs. According to Freire, it is not pathogenic for these 

 animals in the winter months, but in summer, at Rio de Janeiro, it is fatal 

 to guinea-pigs and to small birds. 



212. STREPTOCOCCUS COLI GRACILIS (Escherich). 



Found in the faeces of healthy children on flesh diet not during the 

 period of nursing (Escherich). 



Morphology. Micrococci, from 0.2 to 0.4 n in diameter, usually in S- 

 shaped chains containing from six to twenty elements. In agar cultures the 

 chains are shorter, and upon potato they are rarely seen; the elements in a 

 chain are often elongated and show indications of commencing transverse 

 division. 



Biological Characters. An aerobic and facultative anaerobic, liquefy- 

 ing streptococcus. Grows rapidly in the usual culture media at the room 

 temperature. Upon gelatin plates the colonies are at first small, spherical, 

 and well defined, later bulging and lying at the bottom of a funnel of Hque- 



