OBTAINING LARGE AMOUNTS OF HUMAN BLOOD 



35 



5. Loosen the tourniquet, withdraw the needle quickly, and seal the 

 wound with a touch of flexible collodion. 



FIG. 15. METHODS FOR SECURING BLOOD BY PUNCTURE OF A VEIN. 

 The middle figure shows distention of the veins of the arm about the elbow. The 

 needle is entered by a quick upward thrust. Practically any prominent and firm 

 vein may be used. The upper right-hand figure shows collection of blood in a test- 

 tube. Usually 10 c.c. or more are easily collected before clotting occurs. To secure 

 large amounts, use a larger needle with a smooth bore (preferably a platinum-iridium 

 needle). The lower right-hand figure shows collection of blood in a Keidel tube. 



6. Instead of a syringe, the 5 c.c. vacuum bulb devised by Keidel 

 has proved quite satisfactory (Fig. 16). This apparatus consists of a 



