330 AGEICULTUEAL AND INDUSTBIAL BACTEKIOLOGY 



Bacteriological Diagnosis. — It has already been noted 

 that the disease produced by the meningococcus is differen- 

 tiated from the other types of meningitis by identifying 

 the organisms by means of lumbar puncture. , They may 

 usually be identified in a Gram-stained preparation. They 

 may also be grown upon suitable culture media. 



At least two relatively distinct types of meningococci 

 have been described, some investigators insisting that there 

 are even more, perhaps four. This is of importance because 

 antisera prepared against one type does not appear to be 

 particularly efficacious against another type. It is advan- 

 tageous in some instances to determine the type of meningo- 

 coccus causing the disease in the particular individual. 

 Pure cultures may be secured and tested by the agglutina- 

 tion reaction against serum specific for each of the meningo- 

 coccus types. 



Immunity. — The problem of immunization against 

 meningococcus is complicated, as is the case with the 

 pneumococcus, by the fact that there are two or more dis- 

 tinct varieties. Antisera containing antibodies specific for 

 the disease have been used with a marked degree of success. 

 The antisera are prepared by injecting dead and, later, liv- 

 ing cultures of meningococci into a suitable animal, such as 

 the horse. When a high degree of immunity has been 

 secured the horse is bled, the blood serum secured and fil- 

 tered. -This is usually injected intraspinally, that is 

 cerebrospinal fluid is removed and a sufficient amount of 

 the antiserum introduced. This comes in immediate con- 

 tact with the microorganisms growing on the meninges. 



