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.—1. 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 ihe patient on his left side and find the pro- 
cesses of the second, third, and fourth lumbar vertebre. 
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. 
