Directional left-sided asymmetry of adrenals in experimentally domesticated animals

Directional left-sided asymmetry of the adrenals was typical of black and silver foxes, American minks, and gray rats selected by their behavior. In domesticated, but to a greater extent, in aggressive animals, the weight of the left adrenal and the width of its medulla and cortex markedly surpassed the corresponding parameters of the right adrenal. In aggressive animals enlargement of the left adrenal cortex was associated with widening of the zona reticularis, while in domesticated animals with enlargement of the zona fasciculata.