WIDAL SERUM TEST 87 



cool place. Experimentally, it is easily obtained by immu- 

 nizing a guinea pig and then drawing the desired amount of 

 blood from a vein. 



Blood serum may be obtained by filling a small (capillary) 

 glass tube with the fresh blood, sealing it, and allowing it to 

 stand until the serum collects on the top, when the tube may 

 be broken and the serum drawn off with a fine-pointed pipette. 



