CHAPTER XVI 



THE TECHNIQUE OF SERUM REACTIONS 



Obtaining Serum from Animals and Man. To obtain blood serum 

 from man, the blood may be taken from the finger or the ear, either 

 into a sterile centrifuge tube or into a Wright capsule. When taken 

 into a centrifuge tube, the blood is allowed to clot and the serum 

 separated by centrifugation. Larger quantities of blood may be 

 taken with a syringe from the median basilic vein and either slanted 

 in sterile test tubes in the ice chest or put into centrifuge tubes 

 and centrifugalized. In bleeding small laboratory animals, a number 

 of methods may be employed, depending upon the quantity of serum 

 required. 



The animals most frequently used for laboratory purposes are 

 rabbits. To obtain small quantities of serum from rabbits, the 

 animals may be bled from the marginal vein of the ear. The animal 

 is strapped upon a tray and underneath it is placed "a rubber bag 

 filled with warm water. This is advised by Wadsworth to facilitate 

 the flow of blood. The tray is then placed upon an easel so that 

 the animal's head hangs downward. The skin over the ear vein 

 is shaved and sterilized, and a Hagedorn needle plunged into the 

 vein. The blood is caught in test tubes or centrifuge tubes. 



When larger quantities of blood are desired it may be taken from 

 the carotid artery. In rabbits, the carotid may be found lying just 

 lateral to the trachea and deeply placed, and must be carefully 

 separated from the pneumogastric nerve by blunt dissection. The 

 distal end of the artery is then tied off and the proximal end tem- 

 porarily closed with a small clamp. The artery is then raised out 

 of the wound on a knife or forceps handle and, with sharp-pointed 

 scissors, a small incision is made into but not through the vessel. 

 A small glass cannula is now introduced and tied into place by a 

 thread. To this cannula a small rubber tube fitted with a pinch-cock 

 should have been attached, the whole being sterilized. Recently 

 we have dispensed with the cannula, simply holding the vessel up 

 with a pointed forceps. A larger yield of serum will be obtained 



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