SYMPOSIUM ON AVIAN LYMPHOMATOSIS AND ALLIED DISEASES 103

IT HAS been known for a long time that resistance to infectious diseases, in many cases, has been dependent upon hereditable differences. Indeed Hypocrates stressed the fact that some individuals are endowed with a greater constitutional re-sistance than others. Today practicing physicians regard certain families of in-dividuals among the human race as pos-sessing marked ability to "ward off " cer-tain prevalent infections. Mohr (1934) in "Heredity and Disease " discusses this phase of heredity and resistance to in-fections affecting the human race in a most interesting manner. The resistance of sheep and horses to tuberculosis and similar types of resistance among various other domestic animals has been known to exist for a long time. Hereditary resistance to abortion was found to exist among cer-tain strains of rabbits at the Wisconsin Station. Perhaps the first scientific report of hereditary resistance to a specific poultry disease was that of Frateur, who reported at the 1924 World's Poultry Congress upon a probable genetic basis of resistance to fowl diphtheria. At the 1930 Congress, Card and Roberts reported that resistance to pullorum disease existed in the fowl and their subsequent work has given us a very careful genetic analysis of the prob-lem. The Iowa investigators, in numerous publications from 1928 up to the present, have reported on hereditable resistance to typhoid. The Kansas workers have re-ported a possible genetic difference in re-sistance to roundworm infestation, while the Cornell workers have reported breed differences in resistance to vitamin Bl de-ficiency. Inheritance of resistance to fowl paralysis was reported by Asmundson and Biely in 1932. Their work showed that differences in susceptibility to paralysis existed among the progeny of different families. Evidence substantiating their findings and indicating the possibility of breeding for resistance to the paralysis complex has been added particularly b