“…Medawar (19Uii), from his work with rabbits, hypothesized that at least seven independently-combined antigens are responsible for skin graft reactions and says there are at least 23 such groups in man, Oorer (1938) felt that antigenic differences were determined by dominant genes, Loeb and Wright (19U7) concluded that the genes prt;sent in the host of a transplant determined its success or failure, Snell (I9li8), on the basis of his work with mice, estimated that there were six to lU gene loci involved in determining the fate of tumor transplants. /"Hesselberg and Loeb (19l8)j Loeb (1902), (1902), (1918), (1918), (1920), (1921), (1930), (1930 Loeb and V^tight (1927), found that tumor transplantation in mice from hybrid to parental strain gave negative resixlts as far as the nunber of takes was concerned, while reverse transplantation gave 100 per cent takes.…”