142 MODERN BIOLOGIC THERAPEUSIS 



lumbar spine, and the point of election is mid- 

 way between this spine and the one immediately 

 below it. The needle should be cautiously 

 pushed forward until the slight resistance of 

 the dura is felt; this occurs at a depth of about 

 two centimeters (% inch) in infants, and at 4 

 to 6 centimeters (l^X. to 2 inches) in adults. If 

 bony resistance is encountered, withdraw the 

 needle slightly and change the angle of inser- 

 tion. As soon as the dura has been punctured, 

 the stylet should be withdrawn, and cerebro- 

 spinal fluid will begin to flow from the needle. 

 Cerebrospinal Fluid The fluid is usually 

 cloudy or turbid, and escapes slowly; if there is 

 no flow, or if the flow ceases too soon, the needle 

 may be rotated or its lumen freed by the intro- 

 duction of the stylet, or the needle may be in- 

 troduced a trifle further. The fluid should be 

 allowed to flow from the needle into a sterilized 

 test tube, and should be examined bacteriologic- 

 ally to determine the presence of meniugococci. 

 However, the serum should be injected imme- 

 diately without waiting for bacteriologic exam- 

 ination ; but a second injection of serum is not to 

 be given until examination of the cerebrospinal 

 fluid shows the presence of the meningococcus. 



