106 MODERN BIOLOGIC THERAPEUSIS 



soap and water and followed by alcohol and 

 ether. The operator, whose hands have been 

 sterilized, takes the sterilized needle with its 

 contained stylet in his right hand and intro- 

 duces the needle through the intervertebral disc 

 between the third and fourth lumbar vertebrae, 

 and a little to one side of the median line; the 

 thumb of the left hand being placed between the 

 spinous processes as a guide. The point for 

 inserting the needle may be conveniently lo- 

 cated by placing the index and third fingers of 

 the left hand on the highest points of the iliac 

 crests. The middle finger will then rest on the 

 third lumbar spine, and the point of election 

 is midway between this spine and the one im- 

 mediately below it. The needle should be cau- 

 tiously pushed forward until the slight resist- 

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

 of about two centimeters (% inch) in infants, 

 and at 4 to 6 centimeters (I 1 /, to 2 inches) in 

 adults. If bony resistance is encountered, with- 

 draw the needle slightly and change the angle 

 of insertion. As soon as the dura has been 

 punctured, the stylet should be withdrawn and 

 as much cerebrospinal fluid allowed to flow 

 from the needle as possible. 



