The topogenesis of the thyroid in chick embryos.

Using the technique of linar marking on the embryonic thyroid of chicken, it was proven that the thyroid anlage after its evagination from the primitive pharynx, does not undergo any caudal migration. Its topogenesis is influenced by two main mechanisms. First, the relative craniocaudal displacement follows from the cranially oriented growth of the neck and second, the enlarging oesophagus presses the trachea ventrally against the thyroid anlage promoting its division and separation of both lobes.