Iodine Deficiency and Goiter. One of the outstanding discoveries in the field of nutrition in recent years is the relation of deficiency of iodine in food and water to the incidence of simple goiter. Numerous losses of young farm animals throughout the Great Lakes region northwestward into Montana and elsewhere have been due to this cause. The soil in these goitrous regions is practically free from iodine so that plant products grown thereon do not contain it. Injury from iodine deprivation results before birth as well as after. The administration of a suitable amount of iodine to the human population in goitrous areas bids fair to correct this trouble. Kimball has emphasized the inadequacy of iodine therapy for infants born of mothers whose thyroids were deficient in iodine. He points out that the thyroid under these conditions is injured in pre-natal life and that subsequent provision of iodine will not prevent some abnormality in the gland. The importance of keeping the expectant mother's thyroid provided with iodine is, therefore, apparent.

Secondary Anemia and Iron Assimilation. Secondary anemia may be due to excessive hemorrhage, hookworm, chemical poisoning, etc. The impoverished blood tends to return promptly to normal when an adequate diet is provided. An interesting discovery made by Hart and co-workers relates to the conditions under which iron can be assimilated and converted into the respiratory pigment of the red blood corpuscles. They have shown that iron assimilation is impossible in the absence of a small quota of copper in the body. When the diet is entirely adequate in every respect, including copper, inorganic iron salts are capable of utilization for hematin synthesis. The relative values of iron salts depend only upon their solubility; although it was demonstrated some years ago that, if ferrous salts are introduced into the food, oxidation of vitamin A by the air is strongly catalyzed. For this reason animals may be fed an adequate amount of A, but if the iron is in the ferrous form, the vitamin A may be destroyed and the animals will then develop the typical ophthalmia of dietary origin.

Until recently, pernicious anemia did not yield to any form of treatment. Minot and Murphy discovered that when pernicious anemia patients are given large amounts of liver daily, the blood stream promptly improves and the anemia disappears in great measure. The disease is not curable; and liver, or a suitable preparation from it, must be taken throughout life, otherwise a return of the anemia is certain.

All pernicious anemia patients have a long history of digestive disturbances terminating in a loss of capacity of the stomach to produce hydrochloric acid. It has been shown that in the digestion of meat in the normal stomach something is formed which is indispensable to the proper functioning of the structures in the bone marrow which form red blood corpuscles. The capacity to produce this substance is lost by the debilitated stomach of the patient with pernicious anemia. It appears that this substance formed in the stomach is largely absorbed in the intestine and tends to accumulate in the liver; but a portion passes on to the general circulation and tends to accumulate in the kidneys. The kidneys are not so good as liver for the relief of pernicious anemia, but are greatly superior to the muscle cuts of meat. The fresh stomachs of pigs, when ground and allowed to self-digest for a while before being cooked, are highly effective as a source of the substance furnished by liver. Several manufacturers are now putting on the market concentrated extracts of liver which are as effective as liver itself in improving the condition of the blood of pernicious anemia patients. The nature of the substance is still unknown.

Supplementary Values in Proteins. Chemical analyses of proteins isolated from various animal and plant sources have revealed a surprising difference in their constitution. Human muscle contains about 12 per cent of a digestion product called glutamic acid. Wheat proteins yield as much as 45 per cent of this substance. This is an example of a food protein yielding an excess of one of the digestion products. There are many illustrations of food proteins yielding too little of one or more digestion products which are necessary for the formation of body proteins. The quality of the protein is determined by its content of that indispensable amino-acid which is present in the smallest amount. Because of the excess or deficiency in the yields of amino-acids, most food proteins of vegetable origin are not of very high quality - that is, these food proteins cannot be transformed with high efficiency into animal proteins. The farm pig fed only wheat proteins can transform about 23 per cent of them into pig protein, whereas it can transform about 65 per cent of the proteins of milk into pig protein. Since proteins differ so widely in their composition, it is frequently found that combinations of two or more proteins from different sources have a higher biological value than either one fed singly. This is because they are not equally deficient in any one amino-acid. Feeding tests have shown that the proteins of the different cereal grains tend to be deficient in the same digestion products, and, accordingly, the combination of wheat and corn, of wheat and oats, or of corn and oats proteins does not enhance the value of the mixture. The protein mixture is not enhanced by combining pea or bean proteins with any cereal grains or by combining pea and bean proteins alone. On the other hand, the proteins of eggs, meat, and milk are especially rich in those digestion products which are furnished in but small amounts by most vegetable proteins. Hence, combinations of these proteins of animal origin with cereal or other vegetable proteins make mixtures of high biological value. The proteins of the leaves of plants are so constituted as to enhance markedly the proteins of cereals, peas, beans, and other seeds of plants.