320 IMMUNOLOGY 



of antibodies would be produced for each kind of cell antigen ; the 

 amount of antibody response would correspond to the amounts of 

 various antigens present. The major antigen would lead to the 

 production of a major or chief agglutinin, while minor agglutinins 

 would be produced for the corresponding minor antigens. Land- 

 steiner (1936) in an excellent discussion of antigens considers 

 cellular antigens as forming a mosaic pattern. This has been dis- 

 cussed in the preceding chapter. 



Precipitins and Specificity. — Shortly after Gruber and Dur- 

 ham's discovery of specific and group agglutination of bacteria, 

 Kraus (1897) reported that filtered extracts of bacteria would 

 give specific precipitates when mixed with their homologous im- 

 mune serum. Two years later Tchistovitch (1899) found that 

 blood serum (eel) when used as an antigen led to the production 

 of precipitins in rabbits. There followed, according to Pick (1904), 

 extensive investigations of antigens as to their nature, method of 

 preparation, chemical and physical structure, and specificity. Nut- 

 tall (1904) used quantitative precipitin tests in an extensive study 

 of the zoological relationships in the animal kingdom. His results 

 were in harmony with the accepted zoological relationships which 

 had been based upon morphology. This indicated that the process 

 of evolution included biochemical as well as anatomical and 

 morphological changes. 



Precipitins and Species Relationship.— While the work of 

 Nuttall (1904) and others indicated that the precipitin test could 

 be used to identify the blood proteins of a species (species specificity 

 parallels immunological specificity), a discovery had been made 

 by Landsteiner (1902) which seemed to be at variance with this. 

 He found that he could differentiate 3 or 4 groups within the 

 human species by means of isohemagglutination. 



Serological Types Within a Species. — Thus while Nuttall and 

 others had shown that the serum proteins of all members of a 

 species were alike antigenically, Landsteiner had shown that the 

 red cells of different groups of individuals within the species 

 (human) were antigenically unlike and that the dissimilarity 

 probably had an hereditary basis. 



Bacterial Types Within a Species. — In 1909, Neufeld de- 

 scribed antigenic differences in a bacterial species, the pneumo- 



