1/8 CLINICAL BACTERIOLOGY AND H^MATOLOGY 



tions upon this point, the most suitable is solidified blood- 

 serum, but in default of this ordinary agar will answer well. 

 (See also the section on cerebro-spinal fever.) 



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

 teriological examination from other parts of the body, it is 

 better if the skin can be sterilized some hours before the 

 operation, and a pad soaked in an antiseptic fluid kept on the 

 area until the last moment. This is usually impracticable, and 

 the process will be described as if it were performed at a single 

 visit. 



If not already sterilized, start the needle boiling and pro- 

 ceed to the disinfection of the patient's back. When the 

 needle has boiled for five 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 processes 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. Sterilize the skin with tincture of iodine; 

 it will be found a great advantage to clear off the pigment 

 with acetone, as the landmarks will thereby be rendered more 

 easily recognized. 



2. Operation Position. Get the patient (still lying on his 

 left side) to draw up his knees so as to flex his back some- 

 what, and to turn partly over on to his face. 



Identify the processes of the third and fourth lumbar verte- 

 brae, and mark the centre of the space between them by means 

 of the index-finger or thumb of the left hand. If local 

 anaesthesia is to be employed freeze the skin round a point 

 about J inch to the right of the middle line, opposite the spot 

 marked by your left finger or thumb. Take the needle in the 

 right hand, holding it like a pen, and enter it at a point level 

 with the centre of the interspace, and I centimetre (a little less 

 than J inch) to the right of the middle line. Direct it for- 

 wards, slightly upwards, and slightly inwards, and press it in 

 with a steady and uniform pressure; this must be applied 

 accurately in the axis of the needle, or the latter may bend 

 and take a wrong direction. 



If the needle strikes against bone withdraw it almost com- 

 pletely, and push it on again after changing its direction 

 slightly. If bone is again encountered it may be advisable to 



