292 A MANUAL OF BACTERIOLOGY 



on the ninth day and the serum preserved : such a 

 serum will probably have a titre of 1-1,200 or there- 

 abouts. 



For agglutination tests, the organism is grown on a 

 legumin agar plate for twenty-four hours at 37 C., the 

 growth is emulsified in saline and the saline suspension 

 for the test is standardised to contain 2,000-4,000 million 

 cocci per cubic centimetre. For the test, the macro- 

 scopic method is employed, the tubes containing the 

 mixtures are kept at 55 C., and the readings taken at 

 the end of twenty-four hours. 



By the application of agglutination and saturation 

 tests the meningococcus has been differentiated into at 

 least four types or races. The method employed was as 

 follows : A series of meningococci from the cerebro -spinal 

 fluid of thirty-two cases of cerebro -spinal fever having 

 been collected, an agglutinating serum was prepared with 

 one of them, and all the thirty-two strains were tested as 

 to agglutination with it. The result was that nineteen of 

 the strains agglutinated well and three only slightly. 

 They were all further tested by the saturation test, with 

 the result that all the nineteen strains which agglutinated 

 well absorbed agglutinin, while the remaining thirteen, 

 including the three which agglutinated only slightly, 

 failed to absorb agglutinin. The nineteen strains which 

 agglutinated and absorbed were grouped together as 

 type I. 



Type II was differentiated by taking one of the thirteen 

 strains which were excluded by the first test, preparing a 

 second agglutinating serum with it and testing all the 

 thirty -two strains with this second serum. Although 

 twenty -one of the strains showed some agglutination, this 

 was well marked in the case of seven of them only. On 

 applying the absorption test, all of these seven cocci, and 

 also one of the cocci that had agglutinated only slightly 



