172 IMMUNOLOGY 



glutiiiin content of each group of both the new classification and 

 that of Jansky and hence can readily determine the same for the 

 groups of Moss. 



Time of Appearance of Agglutinogen and Agglutinins. — Since 

 the discovery of the blood groups of Landsteiner, numerous in- 

 vestigations have uncovered many interesting facts relative to 

 the factors involved in isohemagglutination. It has been shown, 

 for instance, that the agglutinogen content of the red cells is, as 

 a rule, complete at birth. On the other hand, the agglutinins 

 may or may not be present in the serum at birth, but may make 

 their appearance at some time during the first four years of life. 

 After the isohemagglutinating factors of a blood are complete, 

 there is no qualitative change during the lifetime of the individ- 

 ual. It has been shown that disease may increase or decrease the 

 titer and that the titer may drop during the later years of life, 

 but the group, when once determined, remains constant. A 

 number of individuals have found agglutinins from the maternal 

 blood present in the blood of the child at birth. These usually 

 disappear from the blood stream by the tenth day. Various theories 

 have been offered to explain their presence in the circulation of 

 tlie newborn. It is thought that changes in permeability of ves- 

 sels in the placenta may account for the phenomenon. 



Inheritance of Blood Group Factors. — The first evidence sug- 

 gesting that the blood group factors might be inherited was pre- 

 sented by Epstein and Ottenberg (1908). They typed a mother 

 and seven sons of one family and four sons and both parents of 

 another family. All members of the first family were found to 

 be in group A, while all members of the second family were in 

 group B. Two years later, von Dungern and Hirschfeld (1910) 

 obtained data on seventy-two families covering tAvo generations 

 and 248 individuals. From an analysis of this data, according to 

 Ottenberg* (1928) and Snyder (1929), they concluded: "(1) A 

 or B never occurs in the red cells of a child if not present in one 

 of the parents. (2) When one of these substances is present in 

 both parents it occurs in most of the children. (3) When only 

 one parent has one of these particular substances, some of the 



•ottenberg and Bere;; : Newer Knowledge of Bacteriologrj- and Immunology, 

 Jordan and Falk, Univ. of Chicago, 1928, p. 909. 



