EXAMINATION OF CEREBRO-SPINAL FLUID 73 



of 10-15 c.c. capacity, carefully sterilised, is then plunged 

 obliquely through the skin into the lumen of the vessel. Several 

 cubic centimetres of blood can thus be withdrawn into the 

 syringe. Some of the blood (e.g. 1 c.c.) should be added to 

 .small flasks containing 50 c.c. of bouillon ; the rest may be 

 used for smearing the surface of agar tubes, or may be added to 

 melted agar at 42 C., which is then plated. The flasks, etc. 

 are then incubated. By this method cultures can often be 

 obtained where the former method fails, especially in severe 

 conditions such as ulcerative endocarditis, streptococcus infection, 

 etc. Part of the blood may be incubated by itself for twenty- 

 four hours, and cultures then made. Needless to say, the in- 

 oculations of media must be done at the bedside, as of course 

 the blood quickly coagulates in the syringe. Coagulation can 

 be prevented by drawing up into the syringe before it is used a 

 quantity of 2 per cent, sterile sodium citrate equivalent to the 

 amount of blood it is intended to withdraw. 



In examining the blood of the spleen a portion of the skin 

 over the organ is sterilised in the same way, a few drops are 

 withdrawn from the organ by a sterile hypodermic syringe, and 

 cultures made. (For microscopic methods, vide p. 94.) 



Bacteriological Examination of the Cerebro-spinal Fluid 

 Lumbar Puncture. This diagnostic procedure, which is 

 often called for in cases of meningitis, can be carried out with 

 a sterilised " antitoxin needle " as follows : The patient should 

 lie on the right side, with knees somewhat drawn up and left 

 shoulder tilted somewhat forward, so that the back is fully 

 exposed. The skin over the lumbar region is then carefully 

 sterilised, as above described, and the hands of the operator 

 should be similarly treated. The spines of the lumbar vertebrae 

 having been counted, the left thumb or forefinger is pressed 

 into the space between the third and fourth spines in the middle 

 line ; the needle is then inserted about half an inch to the 

 right of the middle line at this level and pushed through the 

 tissues, its course being directed slightly inwards and upwards, 

 till it enters the subdural space. When this occurs, fluid passes 

 along the needle, sometimes actually spurting out, and should be 

 received in a sterile test-tube. Several cubic centimetres of 

 fluid can thus usually be obtained, no suction being required ; 

 thereafter it can be examined bacteriological ly by the usual 

 methods. The depth of the subdural space from the surface 

 varies from a little over an inch in children to 3 inches, or 

 even more, in adults the length of the needle must be suited 

 accordingly. In making the puncture it is convenient to have 



