ANTIBODIES I 



Fig. 1-1. Photographs of the precipitin reaction. Reading from left to right: 

 negative reaction, weak positive reaction, strong positive reaction. These tests 

 were carried out by the interfacial technique — placing a layer of diluted antigen 

 over a layer of immune serum in a test tube). 



Fig. 1-2. Photomicrographs of unagglutinated red blood cells (left) and 

 agglutinated cells (right). 



