MINERAL METABOLISM 327 



fresh substance; iron is likewise found in bone marrow and in muscles. 

 As a constituent of nucleoproteins iron has the function of a catalyst 

 (Spitzer) particularly of oxidations, and its presence in most (Mouneyrat ; 

 Jones) if not in all cells (Masing) both animal and vegetable has"gen- 

 erally been accepted. It has been demonstrated in the liver and other 

 organs of animals whose blood pigment is not hemoglobin (Baldoni ; Dastre 

 and Floresco). The cell nuclei of vegetable tissues also contain iron, and 

 the decorticated and enucleated form in which most cereals are used for 

 human food makes them relatively poor purveyors of this element. Some 

 fruits and vegetables, especially the chlorophyll-containing ones, such 

 as spinach and cabbage, are richest in iron. The amount of iron necessary 

 to meet the daily requirements of man cannot be stated dogmatically since 

 it depends on the kind and amount of other foods, organic as well as in- 

 organic, ingested with it (Kochmann(c) ). In view of our meager knowl- 

 edge Sherman in his review of the functions of iron in nutrition states that 

 the daily intake ought to be not less than 12 mg. of food iron, a figure 

 which should be increased during pregnancy and lactation. Milk is one 

 of the poorest sources of iron (Jolles and Friedjung; Langstein ; Edelstein 

 and v. Czonka). The relative amount of iron in the body of an animal 

 varies with its age; thus Meyer (a) showed that in calves the iron of the 

 liver decreases with increasing age; he found that the fetus contained 

 ten times as much iron (relatively) as the grown animal, most of which 

 is accumulated during the last three months before birth (Hugounenq). 

 This question was especially dealt with by Bunge(fr) and Abderhalden 

 (e) (a) (g), who found, in rabbits and in rats, that the relative amounts of 

 iron and hemoglobin in the body decreased progressively during lactation, 

 at the end of which it was at a minimum. Thereafter, on the mixed food 

 of the mother the iron again increased. In guinea pigs whose lactation 

 period is extremely short, this relation was not observed. Abderhalden 

 therefore points out the undesirability of restricting an infant to milk diet 

 beyond the period of lactation, and the necessity of abundant iron-contain- 

 ing foods for growth and increasing blood volume. 



In iron-containing foods the element is usually in complex organic 

 combination ; only in drinking water and in medicinal iron preparations 

 is iron ingested in inorganic form. The course which iron follows in the 

 digestive tract has been of special interest because of a possible difference 

 in behavior between the two forms, and in contradiction to the first pro- 

 nouncements of Bunge( on the toxicity of inorganic iron and the good 

 fortune of its non-absorption there has come a general acceptance of the 

 view that both forms are absorbed in the same way. The toxicity of iron 

 salts given intravenously was demonstrated long ago, but since inorganic 

 iron per os has no toxic effects unless the doses are large enough to erode 

 the epithelium, iron salts are in some way modified in the stomach 

 (Gaule). A part of the ingested iron, either organic or medicinal, is set 



