A New Sub-Lethal Factor in Hens

Abstract

LETHAL—ordeadly—hereditaryfactors are today known among most species of domestic animals. These factors are called deadly because they produce various defects that make the individual incapable of sustained life. If a defect is of such a serious nature that the individual dies at the embryonic stage, the defect is called lethal. If the individual dies shortly after birth, the defect is called sub-lethal. In like manner, one speaks also of lethal and sub-lethal inheritance factors or genes.Lethal defects in domestic animals have been known a long time, but their hereditary relations were clarified only after the turn of the 19th century. Since that time many lethal factors have been reported. According to Professor Tuff, a total of seventy lethal factors have been recorded among domestic animals, including twenty-five among cattle.One of the first lethal factors observed among hens was one reported by Dunn in 1923. Among White .