70 IMMUNE SERA 



blood cells and he found that these were agglutinated 

 and would be agglutinated even when mixed with 

 normal goat serum. Knowing, as he did, that 

 immunization against bacteria increases the agglu- 

 tinating property toward a given organism over 

 that in the normal animal, it was natural that he 

 should experiment to see whether similar results 

 could be obtained with red blood cells. Accord- 

 ingly he injected guinea pigs several times with 

 5 cc. defibrinated rabbit's blood, and found that 

 not only did this guinea-pig serum acquire agglu- 

 tinating properties, but also the property to dissolve 

 rapidly and intensely, in a test-tube, the red blood 

 cells of a rabbit. The serum of a normal guinea 

 pig was incapable of doing this, or did it in only a 

 slight degree. Bordet could further show that this 

 action is a specific one, i.e., the serum of animals 

 treated with rabbit blood acquires this dissolving 

 property only for the red cells of rabbits, not for 

 those 'of any other species of animal. -For the 

 latter, such a serum is no more strongly solvent 

 than the serum of a normal animal. The same 

 property that Bordet had demonstrated in the serum 

 of guinea pigs treated with rabbit blood could now 

 be shown for the sera of all animals treated with 

 blood cells of a different species. We can formulate 

 this as follows: The serum of animals, species A, 

 after these have been injected either subcutaneously, 

 intraperitoneally, or intravenously with erythrocytes 



