a slide test widely used for the diagnosis of infectious mononucleosis, based on the principle that the heterophil antibodies that occur in the serum of patients with infectious mononucleosis are absorbed by bovine red cells but not by guinea pig kidney cells; thus, when equine red blood cells (which provoke heterophil antibodies) are mixed with patient serum and agglutination occurs in the presence of bovine red blood cells, the presumptive diagnosis is infectious mononucleosis.