94 IMMUNITY 



If bloods be compa table no change will occur in the blood cells. 

 If donor's corpuscles be agglutinated by recipient's serum there 

 will be clumping in the first tube; if the reverse, a change will 

 occur in the second tube. This method while often used is more 

 trouble and no more reliable than the following : 



2. It is necessary to have for the group determinations, known 

 sera of the various types, but for practical purposes types II and 

 III will reveal any type corpuscles suspended in them. The blood 

 to be tested is caught from a prick in the finger into a few drops of 

 sodium citrate solution. One drop of this cell suspension is mixed 

 with one drop of type II and of type III sera separately on a slide. 

 After a period of five to thirty minutes clumping may occur. 

 If it occur in both, the blood is by the Moss scale group I; if in 

 neither it is group IV; if clumping occur in serum III and not in 

 serum II, the blood is group II; if clumping occur in group II 

 and not in group III the blood is group III. 



