A glass plate is coated with a layer of agarose gel. A central well and four surrounding wells ( M , N , O , P ) are cut on the agarose as shown in the figure on the right side. A mixture of x and y antibodies is added in the central well that react specifically with antigens X and Y , respectively. Wells M and N contain the antigen X . Wells P and O contain antigens of unknown identity. All the antigens and antibodi