364 BACTERIA PATHOGENIC TO MAN 



frequently outside the cells and is usually spherical or lancet-shaped 

 and frequently occurs in short chains. Sometimes the bacteria are 

 present in very small numbers, and then many smears must be looked 

 through before a probable diagnosis can be made. In all cases absolute 

 certainty can only be obtained through cultures. Here plain nutrient 

 agar, serum agar, and blood-agar plates should be made, and, if desired, 

 tubes also. When considerable quantities are inoculated upon these 

 media and meningococci are present, as a rule, a greater or less number 

 of colonies having the characteristics already described will develop. 

 The value, clinically, of the examination is that about 40 per cent, of 

 the cases due to this coccus recover, while almost all of those due to the 

 pneumococcus and streptococcus die. 



In many cases there are very few diplococci present in the spinal 

 fluid, so that a failure to find them in a microscopic examination 

 should not be taken to prove that the disease was not due to this 

 organism. For cultures a considerable amount of fluid must be used, 

 for we have found, as described by Councilman and others, that 

 there may be very few living diplococci even in 1 c.c. of fluid. 



To obtain the fluid the patient should lie on the right side with the 

 knees drawn up and the left shoulder depressed. The skin of the 

 patient's back, the hands of the operator, and the large antitoxin 

 syringe should be sterile. The needle should be 4 cm. in length, with a 

 diameter of 1 mm. for children, and longer for adults. 



The puncture is generally made between the third and fourth lumbar 

 vertebrae. The thumb of the left hand is pressed between the spinous 

 processes, and the point of the needle is entered in the median line 

 or a little to the right of it, and on a level with the thumb-nail, and 

 directed slightly upward and inward toward the median line. At a 

 depth of 3 or 4 cm. in children and 7 or 8 cm. in adults the needle 

 enters the subarachnoid space, and on withdrawing the obturator the 

 fluid flows out in drops or in a stream. If the needle meets a bony 

 obstruction withdraw and thrust again rather than make lateral move- 

 ments. Any blood obscures the microscopic examination. The fluid 

 is allowed to drop into absolutely sterile test-tubes or vials with sterile 

 stoppers. From 5 to 15 c.c. should be withdrawn. No ill effects have 

 been observed from the operations. On the contrary the relief of 

 pressure frequently produces beneficial results. 



Organisms Exciting Meningitis. 1. The pneumococcus. This diplo- 

 coccus is one of the most frequent exciters of meningitis, not only when 

 it is a primary disease, but also when it is secondary to a pneumonia, 

 otitis, etc. 



2. The streptococcus pyogenes and the siaphylococcus. pyogenes. 

 Meningitis due to these organisms is almost always secondary to 

 some other infection, such as otitis, tonsillitis, erysipelas, endocarditis, 

 suppurating wounds of scalp and skull, etc. 



3. The bacillus influenzT. Numerous doubtful reports have been 

 published of the presence of influenza bacilli in the meningeal exudate. 

 Those that are reliable state in almost every instance that the menin- 



