72 METHODS OF CULTIVATION OF BACTERIA 



sterilised with tincture of iodine, and the hands of the operator 

 should be thoroughly purified. The spines of the lumbar vertebra 

 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 bacteriologically 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 

 either a sterile syringe attached, or to have the thick end of 

 the needle covered with a pad of sterile wool, which is of course 

 removed at once when the fluid begins to flow. It is advisable 

 to use the platinum needles which are specially made for the 

 purpose, as a sudden movement of the patient may snap an 

 ordinary steel needle. 



The Bacteriological Examination of the Naso-pharynx. — A 

 specimen of pharyngeal mucus may be obtained by means of a 

 swab of cotton wool on the end of a metal wire. The wire 

 ought to be longer than that used in the case of diphtheria and 

 bent near the extremity. A tongue depressor is used, the wire 

 is introduced into the mouth, and passed up behind the soft 

 palate and then brought into, contact with the posterior pharyn- 

 geal wall. Care must be taken not to touch any part of the 

 mucous membrane of the mouth. The best method, however, is 

 by means of a simple apparatus introduced by West. This con- 

 sists of a glass tube shaped like- a catheter, in the interior of 

 whigh is a thin wire bearing the swab, the latter being just with- 

 in the end of the tube. The bend of the tube can be used to 

 depress the tongue, or a depressor may be used, and when the 

 tube is sufficiently introduced it is turned up behind the soft 

 palate and the end of the wire is pressed so as to protrude the 

 swab, which is theD brought into contact with the pharyngeal 

 wall. The swab is then drawn back into the tube (as a matter 

 of fact it usually springs back) and the tube is removed from 

 the mouth. We have found the method to be extremely simple 

 and effective. Plates of " trypagar " or other suitable medium 

 should be inoculated at once (this is essential) and placed in 



