218 BACTEEIOLOGY OF THE EYE 



and can produce a meningitis ; it is not, however, the cause of the 

 epidemics. It is distinguished from the Gonococcus by the Gram 

 stain.) 



The Weichselbaum Meningococcus grows only in the incubator ; on 

 gelatine at room temperature it does not grow. 



To be quite certain of the first culture serum media alone should be used. The 

 Meningococcus also grows on glycerine agar, on which medium it can be quite well 

 propagated. Many exudates will only give cultures on serum agar, glycerine agar 

 at first failing. On serum agar the colonies are faintly greyish-yellow, prominent, 

 and moist ; they are 1 to 2 millimetres in diameter, sometimes slightly larger. 

 On glycerine the colonies are more transparent, of an iridescent yellow colour, 

 almost homogeneous, and of a slimy consistency. They are easily distinguished 

 with a low magnification from the more granular and browner colonies of 

 Staphylococci. The growth of the latter is much more profuse, especially on 

 gelatine, and its reaction with Gram's stain is absolutely positive, etc. The 

 appearance is different from that of the Micrococcus catarrhalis (vide supra). 

 Streptococcal and gonococcal colonies are in general flatter and smaller, and their 

 further differentiation is quite easy (by means of Gram's stain, chain formation, 

 form of the cocci, etc.). 



Their differentiation from the Gonococcus is the most difficult. Meningococci 

 certainly grow more strongly on blood-serum and glycerine agar as a general rule ; 

 but as this vigorous growth may occur with some strains of Gonococci, this method 

 of distinguishing the two is not so certain as was thought. 



In bouillon a faint cloudiness occurs with a slight deposit ; when shaken this 

 diffuses evenly. On sugar media growth is freer, but not so white and opaque as 

 that of Mic. catarrlialis. 



No growth on potatoes, nor on gelatine at room temperature. Agglutination 

 tests 1 are of great value in deciding between Gonococci and Meningococci, both of 

 which become diffused on being shaken ; while, as we have seen, the Mic. catar- 

 rhalis always sinks of itself to the bottom. A meningococcal serum of high value 

 will, in the dilution of 1 in 1,500, only agglutinate the Meningococci, not the 

 Gonococci. In doubtful cases (and such cannot always be distinguished in culture) 

 this method is of special value. According to Kutscher, 2 it is still more certain if 

 we agglutinate at 55 C. ; then the Meningococci alone react. Brons in his cases 

 tested the fermentative power with eight different kinds of sugar 3 (dextrose, 

 levulose, cane-sugar, inulin, milk-sugar, galactose, maltose, and mannite). Ten per 

 cent, solutions were added to sterilized Kiebel-Tiemann litmus solution, and then 

 placed for ten minutes in a steam oven ; 5 per cent, normal soda solution was 

 added ; then 1'5 c.cm. of the sugar litmus solution was added to 13*5 c.cm. 

 ascites agar in a Petri dish. After proving sterility the culture was then inocu- 

 lated on it. In the case of Gonococci fermentation (redness of the medium) only 

 occurred with dextrose ; in the case of Meningococcus with dextrose and maltose 

 (stronger) ; Micrococcus not at all. Buchanan (Lancet, 1907) states that glucose 

 is only fermented by Meningococcus. 



It is still to be proved whether these latter differences are constant or not. 



1 Reidel, Berlin, prepares from horses a meningococcal agglutinating serum of high 

 value ; it is sent out in air-tight glass tubes containing O'l, 0'5, and 1 grain of the dried 

 material. The serum is according to the formula of Kolle (Bern). Directions for use 

 accompany it. The Kgl. Institut fur Infections-Krankheiten in Berlin also send out a 

 meningococcal serum of high value (cf. Cent. f. akt., 1907, xxxix., Ref., p. 442). 



2 Deutsche Med. Woch., 1906, p. 1849. 



3 Cf. analogous experiments of Knapp with the bacilli of the diphtheria group. 



