“[Hans Leo] Przibram and [Francis Bertody] Sumner independently discovered that the fur of rats and mice, kept at unusually high temperatures, grows thinner, while the peripheral organs, such as the ears, feet, tail, external genital organs, increase in size. The reverse takes place in animals kept at unusually low temperatures. Under certain circumstances the changes become hereditary, reappearing in offspring bred, born, and reared at mean temperatures.”