308 BA CTERIOLOG Y. 



bacteriological investigation, in order to obtain accurate 

 results. The back of the patient and the operator's 

 hands should be made sterile. The needle should be 

 boiled for ten minutes. The patient should lie on the 

 right side, with the knees drawn up, and with the 

 uppermost shoulder so depressed as to present the 

 spinal column to the operator. This position permits 

 the operator to thrust the needle directly forward rather 

 than from side to side. An antitoxin needle, 4 cm. in 

 length, with a diameter of 1 mm., is well adapted for 

 infants and young children. A longer needle is neces- 

 sary for adults and children over ten years of age. 



"Aspiration of the fluid is not necessary, but some 

 operators prefer to attach a hypodermic syringe to the 

 needle, to aiford a better grasp for the hand. In this 

 case the syringe would have to be detached to allow 

 the fluid to flow. The additional manipulation, and 

 possibly the defective sterilization of the syringe, 

 might impair the subsequent bacteriological examina- 

 tion. 



" The puncture is generally made between the third 

 and the fourth lumbar vertebrae, sometimes between the 

 second and third. The thumb of the left hand is 

 pressed between the spinous processes, and the point of 

 the needle is entered about 1 cm. to the right of the 

 median line. Care must be exercised to prevent the 

 point of the needle from passing to the left of the 

 median line and striking the bone. At a depth of 3 or 

 4 cm. in children and 7 or 8 cm. in adults the needle 

 enters the subarachnoid space, and the fluid flows usually 

 by drops. If the point of the needle meets with a bony 

 obstruction, it is advisable to withdraw the needle some- 

 what, and to thrust again, directing the point of the 



