920 THE HEREDITY OF THE BLOOD GROUPS 



factors described by Landsteiner and Levine are added. The possibility of correlation 

 between blood groups and other inherited characters whose Mendelian mechanisms 

 are known has been sought. Most of the attempts to establish such correlations have 

 given either negative or inconclusive results. There have been several claims of link- 

 age between blood group genes and others. Of these the most important are the 

 claims of linkage with diphtheria susceptibility or immunity.' Critical analysis has 

 shown the evidence to be insufficient to establish linkage.^ But this work should be 

 continued because it offers one of the most fruitful approaches to the determination 

 of the mechanism of heredity in man. 



Some new fundamental questions are opened by the work of Yamakami^ and of 

 Landsteiner and Levine/ who independently demonstrated the presence of the iso- 

 agglutinable substances in human sperm. An interesting situation then arises in the 

 case of a heterozygous man belonging to group A whose sperm though containing ag- 

 glutinogen A may give rise to offspring of group O (which cannot contain agglutinogen 

 A). Unless one assumes that there are two kinds of spermatozoa in the individual's 

 semen, the one containing agglutinogen A and the other not, one must conclude that 

 a spermatozoon can carry genes for a character which is incompatible with a character 

 shown by the spermatozoon itself. 



' Hirschfeld, L. and H., and Brokman, H.: J. Immunol., 9, 571. 1924. 



= Levine, P.: /. Immunol., 10, 283. 1926; Snyder, L. H.: Ztschr. f. Immunitdtsforschiing. ti. 

 exper. Therap., 49, 464. 1926. 



3 Yamakami, K.: /. Immunol., 12, 185. 1926. 



-•Landsteiner, K., and Levine, P.: /. Immunol., 12, 415. 1926. 



