To study the structure and function of antibodies or immunoglobulins, Potter had to determine which antigens they reacted with. Serendipity struck when Myron Leon from St. Luke’s Hospital in Cleveland came for a one-day visit in October 1967, bringing several antigens he wanted to screen. Potter offered his myeloma serum samples, containing a mix of plasma cell tumors and antibodies. The Ouchterlony plates were prepared mixing Leon’s antigens with Potter’s serum, and they went out to dinner to await the reactions. The result, shown to the right, revealed an immunoglobulin reacting to a specific antigen associated with pneumococcus bacteria, a breakthrough revelation.