34 METHODS OF OBTAINING HUMAN AND ANIMAL BLOOD 



4. Steady the skin over the vein, and insert the needle in the direc- 

 tion of the blood-current (Fig. 15). It is more awkward, and of no 

 practical advantage, to puncture in a downward direction toward the 

 hand. The needle should be sharp, and of a size midway between the 

 ordinary hypodermic and a large antitoxin needle, as the former 

 is too small and the latter is unnecessarily large. The blood is then al- 

 lowed to drop into a sterile tube. It is not necessary to attach 



FIG. 13. REMOVING SERUM 

 FROM A WRIGHT CAPSULE. 



FIG. 14. METHOD OF SEAL- 

 ING A WRIGHT CAPSULE. 



a syringe, although 5 to 10 c.c. of blood are obtained more quickly 

 by this means on account of the possible gentle suction. Needle and 

 syringe should be sterilized by boiling. When larger quantities of 

 human serum are required as in auto-serum therapy, a platinum- 

 iridium needle should be used, as coagulation in the needle is less likely 

 to occur; besides, these needles are readily sterilized by heating in the 

 flame. 



