LUMBAR PUNCTURE I37 



Cultural Examination. — The tubes which have been inoculated 

 by allowing the fluid to drop directly on to the surface of the 

 medium are to be incubated for twenty-four hours at the body 

 temperature. Streptococci, staphylococci, pneumococci, and the 

 rarer organisms, will probably have developed by this time, and 

 will have formed colonies such as have been previously described. 

 Weichselbaum's diplococcus forms (on blood-serum) " round, 

 whitish, shining, viscid-looking colonies, with smooth, sharply 

 defined outlines which attain a diameter of i to i\ millimetres 

 in twenty-four hours.'' The colonies on agar are similar, but 

 slightly larger, and the growth may become confluent. 



If no colonies appear on blood-serum or agar at the end of 

 forty-eight hours, the case is probably due to the tubercle bacillus 

 or the gonococcus. In some cases of cerebro-spinal fever the 

 diplococci in the exudate are all dead, and cultures remain sterile. 



Interpretation of Results. 



The discovery of Weichselbaum's diplococcus indicates that 

 the case is one of cerebro-spinal fever. The chief importance in 

 making the diagnosis (apart from the fact that it may throw light 

 upon the occurrence of several cases of meningitis within a short 

 space of time by proving the existence of an epidemic) arises from 

 the fact that the prognosis is decidedly better than in other forms 

 of meningitis. Roughly speaking, about 40 per cent, of cases 

 recover, though frequently with mental or other defects. It is in 

 these cases that repeated lumbar puncture is of therapeutic value ; 

 it should be done whenever pressure symptoms are urgent. In 

 these cases also great benefit can be obtained from vaccine treat- 

 ment. The vaccine should be prepared from the patient's own 

 culture, and its use carefully controlled by frequent examinations 

 of the opsonic index. The method is, of course, useless in very 

 rapid cases, but very good results are obtainable in the more 

 chronic ones. In some the immediate benefit resulting from each 

 injection is most marked. 



Meningitis due to the pneumococcus may arise from dissemina- 

 tion from pneumonia or other pneumonic lesion, by spreading 

 from the middle ear, etc., or may be primary. The examination 

 of the exudate throws no light upon this point, and the cause of 

 the infection must be sought for on ordinary clinical lines. 



Tuberculous meningitis is proved by the presence of tubercle 

 bacilli in the fluid, and is indicated by sterile cultures, absence of 



