The thyroid may be looked upon as the organ evolved for maintaining the same amount of iodine in the blood as there is in sea water. Sea water was our original habitat, since, like Venus, we have all come up out of the sea.
The more intimate study of the composition of the blood has revealed the most astonishing parallelism between it and the compounds of sea water. The blood is sea water, to which has been added hemoglobin as a pigment for carrying oxygen to the cells not in direct contact with the atmosphere, nutrients to take the place of the prey our marine ancestors gobbled up frankly and directly, and white cells to act as the first line of defense. To keep the concentration of iodine in the blood a constant, the thyroid evolved, since there is no iodine in most foods and very little in those which do contain it.
The Birth of Venus~ Sandro Botticelli |