314 



INFECTION AND IMMUNITY 



plain which classification is being referred to, and the serologist 

 ought to see to it that no error arises from misunderstanding. 



The table indicates also that the blood groups can be explained 

 by the existence of two agglutinins, a and /?, and two a'gglutinogens, 

 A and B. How these may determine the reaction, the table makes 

 clear. 



SERA 



o 



Group I constitutes about 8 per cent of human beings. This 

 group is generally said to be capable of receiving blood from group 

 I, II, III, and IV, but may be usedv as a donor only for group I. 

 It is spoken of as a universal recipient, although it is best to avoid 

 this and use the same group, if possible. 



Group II constitutes about 40 per cent of all persons, and may 

 be used as a donor for groups I and II, or may receive from group 

 II and IV. 



Group III, about 10 or more per cent, may be used as donor 

 for group I and III, or may receive from groups III and IV. 



Group IV, about 50 per cent of individuals, may receive from 

 group IV only, but is spoken of as the " universal donor." How- 

 ever, recent writers, especially linger, have warned against the use 

 of the so-called "universal donor" since severe reactions have re- 

 sulted following the use of group IV donors for people of another 

 group. 



In all cases it is always best to try to get a donor of the same 

 group. 



