VIII. 

 NON-PATHOGENIC MICROCOCCI. 



MANY of the saprophytic micrococci and bacilli have already been 

 described in the sections devoted to pathogenic bacteria (Part Third). 

 We propose at present to give an account of the morphological and 

 biological characters which distinguish those microorganisms which 

 have not been shown to possess pathogenic power. But it must be re- 

 membered that in many instances the bacteria described in this and 

 the following sections have not been tested at all, or only very im- 

 perfectly tested, with reference to this point ; and no doubt some of 

 them, if tested upon the various animals usually employed in experi- 

 ments of this kind, would prove to be more or less pathogenic. On 

 the other hand, many of the saprophytes heretofore described as 

 pathogenic only produce marked morbid phenomena in susceptible 

 animals when they are injected beneath the skin, into a serous cavity, 

 or into the circulation in considerable quantities. The experiments 

 of Buchner show that very many of the common saprophytes usually 

 classed as non-pathogenic give rise to a local abscess when sterilized 

 cultures are injected subcutaneously into rabbits or guinea-pigs. In 

 short, there is no well-defined dividing line between the pathogenic 

 and non-pathogenic bacteria, and some of those now described as 

 non-pathogenic, as the result of more extended experiments, will no 

 doubt eventually be transferred to the list of pathogenic bacteria. 



159. MICROCOCCUS FLAVUS LIQUEFACIENS (Flugge). 



Found in the air and in water. 



Morphology. Tolerably large micrococci, in pairs or in irregular groups. 



Biological Characters . Anaerobic, liquefying, chromogenic micrococ- 

 cus. Grows in the usual culture media at the room temperature. Upon 

 gelatin plates forms small, yellow colonies, which under a low power are 

 seen to be spherical or oval, with a finely granular surface and a yellowish- 

 brown color; lines radiate from the centre through a zone of transparent 

 liquefied gelatin to the sharply defined border, and later the colonies, which 

 have a diameter of four to six millimetres, resemble a wagon wheel. In 

 gelatin stick cultures smooth, spherical, yellow colonies form upon the sur- 

 face ; these become confluent and form a yellow layer, which by the slow 

 liquefaction of the gelatin becomes depressed ; at the end of five days the 

 gelatin is liquefied to a depth of about two millimetres and a yellowish, 

 flocculent deposit is seen at the bottom of the yellowish-white fluid. Upon 

 potato a deep-yellow layer with irregular margins is quickly developed. 



