THE TRANSPORTATION SYSTEM 513 



the second and subsequent pregnancies, each of these groups contains the antibody 



Since only 15 per cent of the population for other groups but not for its own, that is, 



are Rh negative, and half of these are the serum of Group A has anti-B but not 



women, the chance combination of an Rh anti-A, Group B has anti-A but not anti-B, 



positive man with an Rh negative woman is Group AB has neither antibodies, and 



not great. Although it is important to know Group O has both. These antibodies are 



the Rh condition of the mother before and naturally present in the serum of people, 



during the pregnancy, it is not sufficiently and their kinds must be known in any case 



important to cause alarm on the part of an before blood can be transfused without 



Rh negative woman who is contemplating possible ill effects, 



marriage to an Rh positive man. The groups are readily determined by 



It is important, however, to know the Rh cross-matching according to the scheme 



factor condition of a young girl about to re- shown in Fig. 19-17, where it is apparent 



ceive a transfusion. Suppose an Rh negative that tire only safe transfusions are between 



girl receives large amounts of Rh positive people of the same blood group. In prac- 



blood in a transfusion. She may develop tice, however, it has been found that this is 



such a high concentration of anti-Rh that not altogether true. Persons with Group O 



it might be impossible for her to ever bear have been called universal donors because 



an Rh positive child. Furthermore, if at it is possible to transfuse their blood into 



some subsequent time another transfusion people with any of the other groups without 



were necessary and she were given Rh pos- ill effects. The reason for this is twofold, 



itive blood again, she would suffer a severe, In tlie first place, the erythrocytes have no 



perhaps even fatal, reaction. Concern for antigenic proteins, so there can be no re- 



the type of transfusions used is not con- action between them and the antibodies 



fined to the female alone. Rh negative males in the recipient's plasma. Secondly, the 



can also suffer severe reactions ff transfused introduced anti-A and anti-B antibodies are 



intermittently with Rh positive blood. As diluted so rapidly by the recipient's plasma 



a result of this recent information, blood that they have very little opportunity to 



is routinely typed for the Rh factor. cause the erythrocytes to agglutinate. Of 



Other blood types. At the turn of the cen- course, if the blood is added too rapidly 



tury, Karl Landsteiner, an American Nobel or in too large quantities, some agglutina- 



Prize winner, gave us the first explanation tion might occur. Like the other blood 



of why people sometimes suffer severely groups studied so far, these groups are in- 



when they are transfused with blood from herited in a definite manner, which will be 



another person. These occasional catastro- considered in a later chapter. 



phies made the blood transfusion business ^ , , , , . 



^ ^, . 1 1 i. u J 1 Other functions of the blood 



a rather risky procedure to be used only as 



a last resort. Landsteiner showed that the Among the many functions of the blood 



red cells of the blood contained two pro- must also be included body defense, pH 



teins, called A and B, and that they existed and temperature regulation, and water 



in people singly, in combination, or not at balance. These will now be briefly consid- 



all. Persons could accordingly be classified ered. 



into groups, depending on the nature of Body defense. In addition to the phago- 

 their blood: those with protein A were cytic action of the leucocytes already re- 

 placed in blood Group A, those with B in ferred to, the blood and tissues of the body 

 blood Group B, those with both proteins employ the antigen-antibody reaction to 

 in blood Group AB, and those with neither destroy invading microorganisms that pro- 

 protein in blood Group O. The serum of duce disease. Bacteria as well as animal 



