AGGLUTININS 51 



tube. The latter is allowed to clot and furnishes 

 the serum; the former is prevented from clotting 

 by the sodium citrate and serves to supply the 

 blood corpuscles. Instead of using sodium citrate, 

 Crile, 1 defibrinates the blood by shaking it in a 

 test-tube with a glass bead, and suspending the 

 blood corpuscles in physiological salt solution. 

 Either method may be used, though with the 

 sodium citrate it is necessary to centrifuge, wash 

 the blood corpuscles, and then resuspend them' in 

 salt solution. The suspensions are usually 5% 

 strength. 



In carrying out the test equal parts of serum and 

 blood suspension are mixed in a small test-tube, or, 

 as Epstein 2 has suggested, in small pipettes such 

 as Wright uses for his opsonic tests. After mixing, 

 the tubes are placed in the thermostat for two hours. 

 At the end of this time most of the cells have 

 usually settled to the bottom and pronounced 

 haemolysis can be seen. For finer grades of haemo- 

 lysis it is usually necessary to allow the tubes to 

 stand over night in the refrigerator. 



Agglutination, when it occurs, is rather prompt, 

 and can be readily observed in the gross by the 

 clumping and sedimentation of the blood corpuscles. 



1 Crile, Hemorrhage and Transfusion, 1909, Appleton and 

 Co., New York. 



2 Epstein and Ottenburg, Archives of Internal Medecine, 

 Vol. iii, page 286, 1909. 



