The Effect of Induced Hypothyroidism on the Genetics of Growth in the Chicken ,

THE current increase in our knowledge of the biological functions of the thyroid gland has revealed its importance in influencing the metabolism and growth of chickens, yet the relationship between the gland and its physiological manifestation has received little attention from a genetical point of view. The experiments to be described deal with some aspects of the genetic relationship between thyroidal activity and growth of chickens. Landauer (1929) reported on a single case of dwarfism in a New Hampshire pullet which had an enlarged aplastic thyroid with no colloid tissue. Mayhew and Upp (1932) and Upp (1932 and Upp (1934) showed that a type of dwarfism which yields bantam-like birds in the S. C. Rhode Island breed is due to a recessive autosomal gene. In none of these latter three reports were the anatomical features of the thyroid gland mentioned nor the findings correlated to the specimen described by Landauer (1929) except . . .