The Washed Leukocytes 



273 



The hands of the patient are washed, and a piece of elastic rubber 

 tubing or some other convenient fillet wound about the thumb or 

 a finger to produce venous congestion. With a convenient lancet 

 (Wright uses a pricker made by drawing a bit 

 of glass tubing or a glass rod to a fine point in 

 the flame) a prick is made about a quarter inch 

 from the root of the nail. From this the blood 

 is permitted to flow into small test-tubes pre- 

 viously filled about three-fourths with 1.5 per 

 cent, sodium citrate solution. The blood and 

 citrate solution are mixed, and the tubes placed 

 in a centrifuge, balanced, and centrifugalized 

 until the corpuscles are collected at the bottom 

 of the tube. The citrated plasma is now with- 

 drawn and replaced with 0.85 per cent, sodium 

 chloride solution, through which the corpuscles 

 are distributed by shaking. The tubes are now 

 again centrifugalized until the corpuscles are 

 collected, when the saline is removed carefully, 

 the last drop from the back of the meniscus. 

 In the corpuscular mass that remains the leuko- 

 cytes form a thin creamy layer on the top. 



The serum to be tested and the normal serum for comparison 

 are secured in the same manner, the former from the patient, the 

 latter from the operator. As it is advisable to wound the patient 



Fig. 96. Tube of 

 blood and citrate 

 solution before and 

 after centrif ugaliz- 

 ing (Miller). 



Fig. 97. Removing last drops of saline solution (Miller). 



but once, the tube for obtaining the serum should be filled at the 

 same time that the citrated blood is taken. 



The blood to furnish the serum is taken in a small bent tube shown 

 in the illustration. 



18 



