The Circulatory System 



181 



whose blood is type A has the agghitinogen A in the corpuscles and the 

 agglutinin b in the plasma. The blood groups are always named after 

 the agglutinogen of the red blood cells rather than from the agglutinin 

 of the plasma. The reactions occurring between the various blood types 

 are best shown in Fig. 53. 



RECIPENT 



Fig. 53. — Relationships of blood groups of man. The agglutinogens in cells 

 are indicated by capitals, the agglutinins in the serum by lower case letters. 

 A "plus" denotes agglutination; a "minus" denotes absence of agglutination. 



It can be seen that the plasma of group AB individuals contains 

 no agglutinin ; therefore it is unable to agglutinize the red blood cells 

 of any introduced blood. Thus individuals of this group are known 

 as universal recipients. In a similar manner, the individuals of group 

 O do not have any agglutinogen in their red blood cells. Their red 

 blood cells cannot be agglutinized by the serum of any other blood group. 

 These individuals are known as universal donors. They can give blood 

 to any individual, but can receive it only from other individuals with 

 group O blood. 



The Rh Factor. — Another important consideration in transfusing 

 blood from one individual to another is the Rh factor. This factor is 

 known as Rh from its original discovery in the Rhesus monkey. In 

 its action, the Rh factor is quite different from the blood types dis- 

 cussed above. The persons having this factor are Rh positive; those 

 without it are Rh negative. This is a true antibody reaction, that is, 

 the introduction of Rh-positive blood into the circulation of an 

 individual with Rh-negative blood will result in the formation of anti- 



