. Biology and man. Biology; Human beings. Ratio per 1000 examined ^M ^H - GOITER DISTRIBUTION IN THE UNITED STATES In the First World War, drafted men from the Great Lakes region and from the Pa- cific Northwest had more goiters per thousand than other groups. The soils in these goiter areas contain relatively little iodine, which the body uses in making thyroxin, the thyroid hormone. It is as if the gland enlarged to keep up production from a diet deficient in iodine bonate. The exoskeletons of crustaceans (lobsters, crabs, and so on) also contain la
. Biology and man. Biology; Human beings. Ratio per 1000 examined ^M ^H - GOITER DISTRIBUTION IN THE UNITED STATES In the First World War, drafted men from the Great Lakes region and from the Pa- cific Northwest had more goiters per thousand than other groups. The soils in these goiter areas contain relatively little iodine, which the body uses in making thyroxin, the thyroid hormone. It is as if the gland enlarged to keep up production from a diet deficient in iodine bonate. The exoskeletons of crustaceans (lobsters, crabs, and so on) also contain large quantities of calcium carbonate. Iodine, which exists in relatively large amounts in sea water, has been found to be essential in the life of land mammals and birds and other classes of animals. We should not have suspected that from the very small amounts actually present in our tissues—about forty parts per million. Iodine appears to be an essential constituent of thyroxin, which is secreted by the thyroid gland, located in front of the neck (see illustration opposite). In some mountainous regions, and in upland areas having moderate or high rainfall, the iodine has been leached out of the soil. The plants seem to thrive about as well here as elsewhere. But the animals that feed on these plants indicate the lack of iodine in their development and in their activities (see page 311). Iron is another element present In relatively small amounts yet absolutely necessary in the metabolism of many species. In animals having red blood, 101. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Gruenberg, Benjamin C. (Benjamin Charles), 1875-1965; Bingham, N. Eldred (Nelson Eldred), 1901-. Boston, New York, [etc. ] Ginn and company
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