TESTS FOR ISOHEMAGGLUTININS AND ISOHEMOLYSINS 313 



technic is especially recommended for rapidity and grouping; the masking 

 of agglutination by hemolvsis is delayed or prevented. This method of 

 grouping should be used in conjunction with the group of Moss as given 

 on page 286. It is necessary to have on hand a Group 2 or Group 3 

 blood, and the laboratory worker should know the grouping of his own 

 blood to be used in this work. Group 2 or Group 3 serum may be pre- 

 served in a sterile condition in the refrigerator for several months 

 without losing agglutinating properties. Group 2 and Group 3 corpus- 

 cles may be preserved for four weeks in the refrigerator by the method 

 of Wohl, 1 who adds 3 drops of blood to each cubic centimeter of a solu- 

 tion prepared by adding 0.5 c.c. of 40 per cent, formaldehyd solution 

 to 500 c.c. of 0.85 per cent, sodium chlorid solution containing 2 per 

 cent, sodium citrate. 



Five or 6 drops of Group 2 blood are collected in a small clean, dry 

 test-tube or centrifuge tube, and 2 drops in another tube containing 

 1 c.c. of 1.5 per cent, sodium citrate in 0.9 per cent, salt solution. The 

 serum and corpuscles of the unknown blood to be grouped are collected 

 in the same manner. The bloods in the dry tubes are allowed to coagu- 

 late, the coagula loosened with a platinum loop, and the sera separated 

 by centrifuging. Sera and corpuscles are now ready for the tests. Two 

 platinum loopsful of serum are mixed with one loopful of corpuscle 

 suspension on a cover-slide and inverted over an ordinary hanging- 

 drop slide ringed with vaselin. Each serum is set up with each corpuscle 

 suspension. Agglutination, if it occurs, takes place at room temperature 

 within five minutes; the slides should be examined at once and at short 

 intervals with a f objective of the microscope, and rouleaux formation 

 must be differentiated from small clumps due to agglutination. 



1 Jour, of Lab. and Clin. Med., 1917, 2, 516. 



