MICROCOCCUS INTRACELLULARLS MENINGITIDIS 525 



diluted carbolic saline suspension to stand for twenty-four hours, 

 increases agglutinability, and recommends this technique if time per- 

 mits. Tulloch 31 has called attention to a number of precautions both 

 in handling of the cultures and the serum for agglutination which seem 

 to us sufficiently important to note. He recommends the use of 

 standardized suspensions of the meningococci as described by Hine, 

 and recommends great caution in the nature of the medium on which 

 the cultures are grown. He advises getting rid of the condensation 

 water in the slants before washing off the growth, owing to the possi- 

 bility of alkaliii or acid reactions in this condensation water. The 

 strength of the phenol in standard suspensions should never be more 

 than 0.5 per cent. Also he warns against getting any of the agar into 

 the suspension because he believes that it may act under certain cir- 

 cumstances as a protective colloid. 



On the basis that moderate heat increases the agglutinability of 

 organisms like the typhoid bacillus and meningococci, the workers in 

 the British Central Laboratory used the routine method described 

 under carrier determination, that is, incubating the serum culture 

 agglutination mixtures in a water bath at 55, for varying periods, 

 usually twelve hours before the final readings are made. Hot air ovens 

 at 55 are not good substitutes because of the great evaporation which, 

 according to Hine, occasionally leads to spontaneous agglutination. 

 (See also section on Carriers.) 



A'gglutinin Absorption Experiments for Meningococcus Typing. 32 

 A thick suspension of the meningococci to be examined, quantity 

 0.5 c.c., is mixed with the various monovalent type sera, 0.5 e.c., dilu- 

 tions 1 to 25, in saline. Similar serum dilutions were set up without 

 suspensions. The tubes are thoroughly shaken, set in the water bath at 

 37 for one hour, and then at room temperature overnight. The tubes 

 are then centrifugalized at high speed until the supernatant fluid is 

 clear. The supernatant fluids of the tubes containing the suspensions, 

 as well as the fluids similarly treated without suspension, now repre- 

 sent serum dilutions of 1 to 50. 



Each suspension-absorption tube now has a serum control which 

 has been exposed to the same temperature in the same dilutions with- 

 out meningococci. From each set of two tubes now other tubes are 

 made, into which 0.4, 0.2, 0.1, and 0.05 c.c. are taken, and with salt 



31 Tulloch, Royal Army Med. Jour., February, 1918. 



32 The description given is that given by the British Medical Research Com- 

 mittee, loc. cit. 



