COLLECTION OF SERUM. 25 



hand is cleaned with alcohol and water, after which a bandage, 

 handkerchief or rubber band is quite firmly tied around this fin- 

 ger. The windings of the bandage, handkerchief or rubber band 

 are started at the base of the finger and run gradually toward 

 the tip of the finger as more turns are put on. In this way there 

 is produced an accummulation of blood in the veins and capil- 

 laries. Now, with the pointed end of the capillary bulb, the fin- 

 ger is pricked at a point about a quarter of an inch back of the 

 nail, the needle end is broken off enough to open the capillary 

 end. The open end "a" is now held close to the drop of blood 

 which gradually fills the bulb; this is indicated in Fig. 5. 



Fio. 5. 



When enough blood has been drawn and collected in the bulb, the 

 bulb is held between the fingers at "a" and "c" and the end"b" is 

 heated and sealed off. As the end "b" cools the blood will draw 

 away from the end "a" and finally all the blood will collect in 

 the bulb proper. After this the bulb is again taken hold of at 

 the curve "c" and by a rapid swing of the arm, as is practiced 

 in shaking down a clinical thermometer, the blood is thrown down 

 into the sealed end "b" as is indicated in Fig. 6. The blood is 

 now allowed to clot in order to expel the serum. The serum 

 may also be separated by hanging the bulb at "c" over the arm 

 of the centrifuge, and centrifuging until the clot and serum have 



