210 Till INTI.RNAL LNVIRONMnNT OF T HF. BODY Part III 



occur in the red cells of dilTercnt persons and that the plasma of the blood 

 contains two kinds of antibodies (agglutinins), a and h. There are four main 

 blood groups among human beings: Group O with antibodies a and b but 

 no antigens is a universal donor; Group A, antibody b and antigen A; Group 

 B, antibody a and antigen B; and group AB, antigens A and B but no anti- 

 bodies in the plasma is a universal recipient (Table 12.3). Many more groups 

 have been described; this is a much simplified statement of complex reactions. 

 The characteristics of blood groups are inherited and remain constant through- 

 out life. 



Table 12.3 

 Results of Mixing Red Cells and Plasma of Human Blood Groups 



Blood Group 



—Compatible; no agglutination 

 -|-Not compatible agglutinates 



Transfusion of Blood 



When more than 40 per cent of the blood is lost within a short period, the 

 body cannot make up the loss. In such a case a transfusion is made, that is 

 an injection into a vein of whole blood, plasma, or serum from another per- 

 son in an effort to restore volume. Great care must be taken to choose com- 

 patible blood to inject into the recipient. Wrong types of blood cells block the 

 capillaries and later disintegrate; the pigment finally fills the tubules of the 

 kidney, ultimately causing death. Blood types are inherited according to 

 Mendelian laws (Chap. 20), and as a child of a blue-eyed and brown-eyed 

 parent may have either blue or brown eyes, so it is impossible to predict 

 the exact blood characteristics of a child from those of its parents. 



Transfusions of whole blood are the only adequate treatment when loss of 

 blood is excessive. The need is usually immediate because cells are necessary 

 to take oxygen to the tissues. The question has always been how to have 



