I Q6 CLINICAL BACTERIOLOGY AND H^MATOLOGY 



Method. Apply the narrow bandage to the upper arm suffi- 

 ciently tightly to obstruct the venous circulation, but not 

 tightly enough to check that in the artery; if the veins do not 

 become prominent, the patient should be made to hang his arm 

 down, and to clench and relax his fist. 



Select a large vein in the antecubital fossa, and choose, if 

 possible, one that is superficial (as shown by its blue colour), 

 not merely prominent, since a deep vein may slip in front of the 

 needle. Avoid, if you can, a vein lying near an artery. Pro- 

 ceed to sterilize the skin in the ordinary way. 



Next take the sterilized syringe and sterilize the point of the 

 needle in the flame of the spirit-lamp. Proceed to make the 



FlG. 33. COLLECTION^OF BLOOD DIRECT FROM 



puncture as shown in the illustration (Fig. 33). Direct the 

 point of the needle away from the patient's body, so that it 

 faces the blood-flow, and enter it at a point about J inch from 

 the vein, at one or other side. (This diminishes the chance of 

 subsequent leakage, and possibly of sepsis, organisms picked 

 up by the needle being wiped off during the passage of the 

 latter through the tissues.) Press it gradually onwards until 

 the needle pierces the wall of the vein, when, in most cases, the 

 blood will rise in the syringe, slowly pressing out the piston 

 before it. If it does not you may make very gentle suction 

 with the piston : it must not be forcible, or the opposite wall 

 of the vein will be sucked in and act as a valve. 



In most cases the only difficulty to arise will be in entering* 



