534 PAT H(Xi UN 1C M ICUOOKU AN ISMS 



tendency to spontaneous agglutination in salt solution and in horse 

 serum. 



MICROCOCCUS FLAVUS. A common inhabitant of the normal throat 

 which grows easily on simple media and may be grown at room 

 temperature at or below 25, temperatures at which the meningo- 

 coccus ceases to grow. It is always important to expose suspected 

 cultures at room temperature in the dark. A yellowish pigment is 

 formed by the cultures, but often does not come out for several 

 days. The very young colonies may very closely resemble meningo- 

 coccus colonies, but are easily distinguished in sub-cultures, es- 

 pecially when the growth is forty-eight or more hours old. There 

 are a considerable number of chromogenic organisms closely related 

 to the Flavus. Elser and Huntoon describe three chief chromogenic 

 groups, one of which has a greenish gray or greenish yellow ap- 

 pearance by reflected light, with an opacity that approximates the 

 meningococcus colony. The second group is the one most closely 

 resembling Lingelsheim 's M. Flavus. 



Their third chromogenic group also makes a greenish yellow 

 pigment, and, except for this, is very similar to the M. catarrhalis. 

 A curious fact has been noted by Elser and Huntoon, namely, that 

 some of their chromogenic organisms were easily distinguishable 

 from meningococcus colonies at first isolation, but in the course of 

 artificial cultivation they lost some of their original characters and 

 their power to produce pigment, and gradually approximate the 

 appearance of meningococcus, at least as it appears in strains long 

 isolated. 



The Flavus group gives pernaps most difficulty in meningococcus 

 carrier examinations, since the young colonies of these organisms 

 may look very much like the young meningococcus cultures. The 

 chief points of differentiation, apart from sugar fermentation, which 

 confirm them, are: The fact that Flavus colonies will grow out at 

 room temperature on slants of simple media; that they begin to 

 form pigment after forty-eight hours or so, and that they will 

 agglutinate in normal horse serum in dilutions often as high as 1 to 

 50, and in the meningococcus sera, indiscriminately, often as high 

 as 1 to 100. Meningococci do not agglutinate in salt solution spon- 

 taneously, unless under the conditions mentioned above as noted by 

 Hine, and under the influence of abnormal acid or alkalin reactions. 

 In all series in which the specific a i>^luti nation test is used for 1he 

 determination of a meningococcus, therefore, normal hoi-sc scrum 



