EXAMINATION BY CULTURAL METHODS 



i55 



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. Proceed 

 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 

 puncture as shown in the illustration (Fig. 31). Direct the point 

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



Fig. 31. — Collection of Blood Direct from Vein. 



blood-flow, and enter it at a point about \ 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 the 

 vein, which may slip in front of the needle if the intravenous 

 pressure is low or the instrument blunt. In this case the vein 



