The point of the needle must be sharp but short. If a needle with a long slender point is employed, only part of the point may enter the membranes; a free flow of cerebro-spinal fluid may then take place, but when the injection is made part of the anæsthetic solution escapes outside the membranes. The needle should he 3½ to 4 inches long and 1 m.m. in diameter. A stylet fits inside the needle and prevents it from becoming blocked during the introduction. To prevent the possibility of rusting, both needle and stylet should consist of hard nickel. The barrel of the syringe must consist of glass so that the appearance of the cerebro-spinal fluid can be seen. The Record type is very satisfactory. The syringe usually supplied for spinal analgesia has a capacity of 2 or 3 c.cm., but one holding 10 c.cm. is more useful. Syringe and needle must be carefully sterilised by boiling in plain water; any trace of soda causes decomposition of the drug. The ampoule containing the tropococaine is sterilised in a strong antiseptic solution so as to avoid the possibility of contamination of the hands when the drug is being transferred to the syringe. _Method of Injection._--The patient should be given a hypodermic injection of ⅛ gr. of morphine and ¹⁄₁₅₀ gr. of scopolamine an hour before the operation. There are a number of minor variations in the method of making the spinal injection, but limitations of space forbid a discussion of theoretical questions and of the relative merits of the different procedures. Only one method, which has been found safe and reliable, will be considered here. The injection is made in the space between the third and fourth lumbar spines, the objective being the mid-line of the subarachnoid space between the two divisions of the cauda equina. The position of the patient is such that the spaces between the lumbar spines are opened up as widely as possible. The most convenient plan is to have the patient sitting on the table with the head and shoulders bent well forward (_see_ Fig. 54.) If the patient is unable to sit up, the injection may be made with him lying on his side, with the knees drawn up and the shoulders bent forward. [Illustration: FIG. 54. Position for the injection. The cross indicates the point at which the lumbar puncture is made--about half an inch from the median plane and in the space between the third and fourth lumbar spines.]