544 PATHOGENIC MICROORGANISMS 



strains in dilutions of 1 to 100. For this reason, 1 to 100 was the 

 dilution adopted for such work in the American Army laboratories. 



One-half c.c. of the bacterial emulsion is mixed with 0.5 c.c. of 

 the polyvalent serum. A control of a similar amount of the culture 

 suspension in 1 to 50 normal horse serum must always be made to 

 guard against spontaneous agglutination. It is always well also, 

 to run a tube with a known meningococcus. 



Since meningococci show a certain amount of resistance to ag- 

 glutination, Gordon has recommended the method in general use 

 during the war, that is, placing the tubes in a water bath at 50 

 for twelve to eighteen hours. Evaporation must be guarded against. 



Olitsky has recommended saving time by growing the organisms 

 in normal horse serum broth directly from the colonies on the plate, 

 discarding all those that grow in a granular form. 



We, ourselves, have used a method that we have not published 

 because we have not had a chance to use it on material on a large 

 scale, which depends upon the thread reaction. Dilutions of poly- 

 valent sera are made in broth tubes, so that the final concentration 

 is 1 to 100. The colony is directly inoculated into this, and in the 

 case of true meningococci grow in granular form. A similar 

 inoculation is made in control tubes of 1 to 50 normal horse serum. 

 These procedures sometimes save time. 



Nicolle in France makes his diagnosis by another method, in that 

 he uses, instead of a dilution of serum, the serum in concentrated 

 form, checking it up with the bacterial suspension, and noting the 

 speed of agglutination. In such concentrations he often gets rapid 

 agglutination of true meningococci in the concentrated serum. 



After the preliminary identification has been made, typing of the 

 meningocococus may be desirable by agglutination against type 

 serum. 



Carriers occasionally will develop meningitis some time after 

 they have been recognized as carriers, showing that the organisms 

 may remain in the nasopharynx for some time, without penetrating, 

 insusceptible individuals. We know of a number of cases in which 

 this seems to have occurred. Gordon mentions a number of cases 

 in which "meningismus" developed among carriers, namely, carriers 

 complained of severe headache, pains in the back of the neck, slight 

 fever up to 102, and slight Kernig. One case he mentions had 

 been in contact for a few hours with a case of cerebro-spinal 

 meningitis, which died within twenty-four hours. It was swabbed 



