The same story may be repeated of the thyroid glands. These consist of two lobes located on either side of the windpipe, just below the larynx (Adam’s apple), and joined together across the windpipe by a narrow band or isthmus of their own substance. Gaskell homologized them with a gland in scorpions, and Mathew says that, if his surmise is correct, “the thyroid represents an accessory sexual organ of the invertebrate.” (_Op. cit._, p. 654.) They are, however, endocrine glands, that generate a hormone known as _thyroxin_, which regulates the body-temperature, growth of the body in general, and of the nervous system in particular, etc., etc. Atrophy or extirpation of these glands causes cretinism in the young and myxoedema in adults. Without a sufficient supply of this hormone, the normal exercise of mental powers in human beings is impossible. The organ, therefore, is far from being a useless vestige of what was formerly useful. George Howard Parker, the Zoölogist of Harvard, sums up the case against the Darwinian interpretation of the endocrine glands as follows: “The extent to which hormones control the body is only just beginning to be appreciated. For a long time anatomists have recognized in the higher animals, including man, a number of so-called ductless glands, such as the thyroid gland, the pineal gland, the hypophysis, the adrenal bodies, and so forth. These have often been passed over as unimportant functionless organs whose presence was to be explained as an inheritance from some remote ancestor. But such a conception is far from correct. If the thyroids are removed from a dog, death follows in from one to four weeks. If the adrenal bodies are excised, the animal dies in from two to three days. Such results show beyond doubt that at least some of these organs are of vital importance, and more recent studies have demonstrated that most of them produce substances which have all the properties of hormones.” (“Biology and Social Problems,” 1914, pp. 43, 44.)