LUMBAR PUNCTURE 185 



Meningitis due to the pneumococcus may arise from dis- 

 semination from pneumonia or other pneumonic lesion, by 

 spreading' from the nasal cavity or 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 bacteria from the stained films, and predominance 

 of lymphocytes. In these cases the fluid often undergoes a 

 very slight coagulation, delicate cobweb-like threads being- 

 observable after some hours. This is in itself strong evidence 

 of tubercle, and if the delicate coagulum can be withdrawn, 

 dried on a slide, and stained by Ziehl-Neelsen's method, there 

 is a fair chance of finding bacilli entangled with it. This is 

 not very easy to do, the best method being to fish it out with 

 a very fine piece of capillary tubing no thicker than a hair. It 

 is easy enough to pick it out with a platinum needle, but 

 almost impossible to get it off the latter on to the slide. 



The other varieti.es of meningitis do not call for special 

 mention. 



The chief value of lumbar puncture to the surgeon is that it 

 enables him to diagnose a concomitant meningitis in cases of 

 lateral sinus thrombosis and cerebral abscess. The fluid usually 

 becomes bloody within twenty-four hours of a fracture of the 

 base of the skull or laceration of the brain. This may assist in 

 the diagnosis or obscure injuries, or of the cause of a case of 

 unconsciousness in which no history can be obtained. 



Haemorrhage into the meninges is indicated by the with- 

 drawal of blood-stained fluid, but it must be remembered that 

 the first few drops may contain a small quantity of blood which 

 has entered the needle during its passage through the tissues, 

 while the rest is clear. When blood from a vein injured by 

 the needle is mixed with cerebro-spinal fluid, coagulation 

 usually occurs if the fluid is allowed to stand, whereas when 

 the blood comes from a haemorrhage this is not usually the 

 case. Blood-stained fluid may occur in meningitis, and should 

 be submitted to a full examination for leucocytes and bacteria. 



