150 CLINICAL BACTERIOLOGY AND H^EMATOLOGY 



Process — i. Preliminary. — As in removal of fluids for bacterio- 

 logical 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. 



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 five minutes, remove the vessel from the 

 flame and allow it to cool without rertioving 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. 

 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. Lastly, 

 pour some alcohol on to the skin of the patient's back to wash off 

 the excess of the antiseptic, or sterilize the skin with tincture of 

 iodine ; in this case 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 somewhat, and to 

 turn partly over on to his face. 



Identify the processes of the third and fourth lumbar vertebrae, 

 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 \ inch) to the 

 right of the middle line. Direct it forwards, 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. 



