ISOHEMAGGLUTININS 187 



The latter, proposed by Bernstein, seems to fit the data at hand. 

 For practical purposes in blood typing the assumption made by 

 Landsteiner that there are two agglutinogens and two corre- 

 sponding agglutinins is quite satisfactory. Evidence is presented 

 indicating that the blood groups are inherited and that in some, 

 but not all, cases of disputed paternity nonpaternity may be es- 

 tablished for certain individuals. 



Attention is also called to tlie existence of subgroups and to 

 the fact that their existence does not interfere with ordinary 

 blood typing. The new agglutinable factors, M, N and P were 

 discovered by Landsteiner et al. Normal agglutinins for M and 

 perhaps for N have not been observed, but a few individuals, 

 representing practically all the groups, have been found whose 

 blood contains an agglutinin for P. This is the same as "extra 

 agglutinin 1" of Landsteiner. Fortunately these reactions dis- 

 appear, as a rule, at temperatures a])o\e 30° C. "Where typing 

 is done at room temperature they may be very rarely encountered. 

 The agglutinable factors present in the blood of lower animals 

 and of the anthropoid apes are also mentioned in connection with 

 their biological significance. 



Various irregular agglutinations are discussed and a definition 

 of "cold agglutinins" is given. 



The antigenic factors of the red cells are discussed. Land- 

 steiner 's views concerning these are developed. Cellular antigens 

 are complex. Two types of specificity exist, one for the species 

 and a second indicating specific differences within a species. 

 The species specific antigens of the red cell are represented by 

 isopliile hemolysins, a nonspeeies specific antigen by the heter- 

 ophile substances. Differences within a species are represented 

 by the agglutinable factors A and B for human blood. The 

 antigenic structure can be thought of as resembling a mosaic. 

 Chemically speaking, the red cell antigens are made up of one or 

 more protein structures and a number of peculiar lipoid-carbohy- 

 drated complexes or haptens. The various haptens such as those 

 for the A factor or the B factor confer definite specificity upon an 

 antigen. The A substances seem to be widely distributed in the 

 tissues of man and animals and even in bacteria. 



