AGGLUTININS 49 



sputum in order to determine when a curative serum 

 should be administered, inasmuch as the curative 

 serum in turn acts only against one strain of the 

 pneumococcus. 



Agglutinins can also be developed against red 

 blood cells and against certain protozoa (trypan- 

 osomes). We speak of the former as hamag- 

 glutinins. Analogous to the haemolytic action or 

 normal serum on the red cells of certain other 

 species, we find that normal serum is able to 

 agglutinate the red cells of many species and bac- 

 teria. For example, normal goat serum aggluti- 

 nates the red cells of man, pigeon, and rabbit; 

 normal rabbit serum agglutinates typhoid and 

 cholera bacilli. 



Of practical interest is the fact that normal serum 

 may agglutinate the red blood cells of another indi- 

 vidual of the same species. Following Ehrlich's nomen- 

 clature, we speak of this as is o agglutination. The 

 subject has been studied by a number of investigators, 

 and mostly in human blood. According to the extensive 

 investigations of Moss, isoagglutinins occur in the serum 

 of about 90% of adult human beings. Landsteiner 

 divided the individuals into three groups, namely : 



Group i. The corpuscles are not agglutinated by 

 sera of the other two groups, while the sera agglu- 

 tinate the corpuscles of both groups. 



Group 2. The corpuscles are agglutinated by the 

 sera of the other two groups, while the sera agglutinate 

 the corpuscles of Group 3, but not of Group i. 



Group 3. The corpuscles are agglutinated by the 



