The Washed Leukocytes 



281 



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 previously filled about three-fourths 

 with i.s per cent, sodium citrate solution. 

 The blood and citrate solution are mixed, 

 and the tubes placed in a centrifuge, balaiiced, 

 and centrifugaUzed until the corpuscles are 

 collected at the bottom of the tube. The 

 citrated plasma is now withdrawn and re- 

 placed 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 saUne is removed care- 

 fully, the last drop from the back of the meniscus. In the cor- 

 puscular mass that remains the leukocytes form a thin creamy 

 layer on the top. 



P'ig. 92. — Tube of 

 blood and citrate solu- 

 tion before and after 

 centrifugalizing (Miller). 



Fig. 93. — Removing last drops of saline solution (Miller). 



The serum to be tested and the noimal 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 

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

 same time that the citrated blood is taken. 



