462 BACTERIOLOGY. 



Small quantities of human blood can be obtained in the 

 following' manner: A piece of rubber tubing is tied above the 

 ■elbow in order to compress the surface veins. On strongly 

 flexing the arm, the superficial veins on the extensor surface 

 will stand out prominently. The median cephalic, or 

 basilic veins can also be used. The surface of the skin 

 over one of these large veins should be thoroughly washed 

 and disinfected. The hypodermic syringq (2 c.c), provided 

 with a wide needle, is sterilized by boiling' in water for 15 

 minutes. When cold, the needle is inserted into the vein 

 without the slightest difficulty. The piston is then slowly 

 withdrawn and the syringe fills with blood. As the needle 

 is withdrawn the opening is closed with the finger and 

 ■eventually an antiseptic compress and bandage is applied. 



Scarcely any pain is experienced by the subject and the 

 operation is borne a great, deal better than if a lance were 

 used. A quantity of sterile blood can thus be obtained in a 

 few minutes. 



In order to obtain serum for testing the agglutinating 

 power, or for other purposes the blood is at once forced out 

 into a centrifuge tube. It should be thoroughly whipped 

 with a narrow glass rod and finally centrifugated: The 

 clear serum is then taken up in a pipette and tested. 



The blood of the horse can be obtained readily, and in 

 large quantity, by introducing a trochar into the jugular 

 vein. This method of bleeding is followed in the prepara- 

 tion of antitoxin. The operation is carried out under asep- 

 tic conditions and hence the blood-serum, thus obtained, is 

 sterile. The method of procedure is essentially that given 

 on p. 268. ^ The trochar is connected by means of a sterile 

 rubber tube with a short glg,ss tube. This is passed into 

 the sterile cylinder or battery jar. The latter should be 

 covered with a double layer of paper before sterilization. 

 The outer paper is then removed and the glass tube is 

 punched through the inner paper cover. Prom 4 to 6 liters 

 of blood can be drawn from a horse at one bleedingl 



