128 BACTERIOLOGICAL DIAGNOSIS. 



Lastly, pour some alcohol on to the skin of the patient's 

 back to wash off the excess of the antiseptic. 



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. 

 It is scarcely necessary to say that the operator must 

 not touch the patient, as his hands have now been 

 sterilised. 



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 one-third of an 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 cm. (a little less 

 than one-third of an inch) to the right of the middle 

 line. Direct it forward, 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 

 completely and push it on again after changing its 

 direction slightly. If bone is again encountered it may 

 be advisable to try again in the interspace between the 

 second and third processes. 



3. Collection of fluid, and inoculation of media. The first 

 few drops of fluid which escape may be stained with 

 blood ; in this case it should be rejected. Allow a few 

 drops of the fluid to flow directly on to the surface of the 

 media without touching the glass. Collect also some of 

 the fluid (1-4 drachms) in the sterilised empty tube. 



