LUMBAR PUNCTURE 151 



If bone is again encountered it may be advisable to try again in 

 the interspace between the second and third processes. 



If the patient is able to do so without harm, it is much easier 

 to perform the operation with him sitting in a chair leaning over 

 the back or on the edge of the bed with his head nearly between 

 his knees, so that the spine is bent into a convex curve ; by this 

 means the spinous processes are rendered more prominent and 

 the spaces between the laminse are made wider (see Fig. 28). The 

 operation is thus made much more easy, and the method is usually 

 preferable in cases of tabes or general paralysis, where the fluid 



Fig. 28.— Operation of Lumbar Puncture with Patient in 

 Sitting Position. 



is collected for a cytological examination only, and the patient is 

 in good general health. But the method with the patient on his 

 side should also be learnt. 



3. Collection of Fluid and Inoculation of Media. — The first few 

 drops of fluid which escape may be stained with blood ; in this 

 case they should be rejected. Allow a few drops of the fluid to 

 flow directly on to the surface of the medium without touching the 

 glass. Collect also some of the fluid (i to 2 drachms) in the 

 sterilized empty tube. If no fluid flows through the needle, it is 

 pyesumptive evidence against the presence of acute meningitis. A 



