LUMBAR PUNCTURE. 127 



possible. The medium required will depend to a great 

 extent upon the nature of the organism which is ex- 

 pected. If there are no indications upon this point the 

 most suitable medium is solidified blood-serum, but in 

 default of this ordinary agar will answer well. If the 

 case is thought to be one of cerebro-spinal fever the 

 most suitable medium for the cultivation of the specific 

 organism (Weichselbaum's diplococcus intra-cellularis) 

 is alkaline 5 per cent, glycerin-agar, and a couple of 

 tubes of this medium should be at hand, as well as 

 blood-serum or ordinary agar. 



Process. i. Preliminary. As in removal of fluids for 

 bacteriological examination from other parts of the 

 body, it is better if the skin can be sterilised some hours 

 before the operation and a pad soaked in an antiseptic 

 fluid kept on the area until the last moment. This is 

 sometimes impracticable, and the process will be de- 

 scribed as if it were performed at a single visit. 



Put the needle to boil in a weak solution of washing 

 soda, and proceed to the disinfection of the patient's 

 back. When the needle has boiled for ten minutes 

 remove the vessel from the flame and allow it to cool 

 without removing the needle. 



Place the patient on his left side and find the pro- 

 cesses of the second, third, and fourth lumbar vertebrae. 

 A line drawn between the upper points of the iliac 

 crests usually cuts the spine at the upper edge of 

 the spinous process of the fourth lumbar vertebra. 

 Scrub the skin in this vicinity with soap and hot 

 water; wash the region with alcohol and then with 

 ether and allow it to dry ; paint on several layers of 

 perchloride lotion, allowing each to soak in before the 

 next is applied ; cover the region with a piece of lint 

 soaked with lotion and proceed to disinfect your hands. 



