42 METHODS OF OBTAINING HUMAN AND ANIMAL BLOOD 



and the constant suction prevents clot formation in the needle. In this 

 manner 5 c.c. of blood may readily be obtained. 



2. Blood may also be secured by aspirating the external jugular vein. 

 The vein is exposed by making a small incision, as in giving intravenous 

 injections. 



3. Sufficient blood to make many complement fixation tests may be 

 secured from a large pig by rubbing the ear vigorously with xylol and 

 making a small incision in the margin. Bleeding is facilitated by at- 

 taching a small test-tube with a side arm to a suction pump. When the 



FIG. 19. METHOD OF BLEEDING A RABBIT FROM THE EAR. 



proper tube is held firmly over the ear, 5 c.c. of blood may be obtained 

 by this method. 



Sheep. 1. Small amounts of blood may be obtained by punctur- 

 ing one of the ear veins. 



OBTAINING LARGE AMOUNTS OF ANIMAL BLOOD 



Rabbit. After immunization of a rabbit has been completed, the 



animal is usually bled to death, the object being to secure the maximum 



quantity of serum in a sterile condition. Various methods may be 



used. The animal should be anesthetized by ether or high rectal 



