36 IMMUNE SERA. 



leaving the agglutinins for the red cells of man 

 and rabbits, etc. 



These experiments of Bordet and Malkoff on 

 the selective combination of the cells show that 

 with the agglutinins as with the lysins (solvent 

 substances) it is a question of numerous substances 

 and not of a single one. When, for example, nor- 

 mal goat serum is able simultaneously to aggluti- 

 nate several, say three, species of blood-cells, this 

 action is not due to a single agglutinin which af- 

 fects all three species, but is the work of three dis- 

 tinct substances, each specific for a certain red 

 cell. 



Nature of the Agglutinins. The agglutinins are 

 fairly resistant substances which withstand heat- 

 ing to 60 C., and lose their power only on heating 

 to 65 C. It is possible, therefore, to make a serum 

 haemolytically inactive by heating to 55 C., and 

 still preserve its agglutinating power. Corre- 

 sponding to the specific combining power of these 

 agglutinins, they possess a haptophore group 

 which effects the combination, and a second group, 

 easily decomposed by acids, which effects the 

 clumping. In the bacterium as well as in the 

 blood-cell there exists a substance not yet closely 

 studied, called the agglutinable substance. This 

 also has two groups, a haptophore, which com- 

 bines with the haptophore group of the agglutinin; 

 and a second, more delicate group, which is acted 

 on by the functional group of the agglutinin. 



