INORGANIC FOODS. 393 



which are capable of absorption in which the iron is too firmly bound to 

 react with such chemicals and thus escapes microchemical detection. It 

 is at least decidedly interesting to know that even under normal conditions 

 of nourishment the tissues of the animal organism always contain iron in 

 compounds which permit its detection by means of the ordinary reagents. 



The mere fact that inorganic iron salts artificially added to the nourish- 

 ment are capable of absorption and deposition in the tissues does not 

 show by any means that this iron is actually assimilated. It would be 

 insufficient to consider the assimilation of iron from the standpoint of blood 

 formation alone. There is no doubt that iron forms an integral part of 

 all cells and tissues of the body. Certainly, this iron in the tissues is just 

 as essential for the normal functions of the separate organs as is the case 

 with the iron in hemoglobin. Some idea of these relations may be ob- 

 tained from the values cited for the iron in the tissues of rabbits during 

 the period of suckling. It is evident from these values that the tissues 

 hold with great tenacity to a definite minimum amount of iron, even 

 when the hemoglobin content of the entire organism is so far diminished 

 that strong anaemia results. At present we have no definite information 

 as to the part played by this iron in the tissues. We do not even know 

 what amounts are present in the separate organs. It is likewise difficult 

 to decide what portion of the total iron has been introduced and what 

 portion is about to be eliminated. Thus it is easy to realize how the 

 question concerning the assimilation of iron has been covered by that 

 of the formation of the hemoglobin. 



At the present time it has never been definitely decided whether the 

 iron introduced into the system in the form of inorganic salts takes part 

 in the formation of hemoglobin or of hematin. We find ourselves here, 

 as is the case with many other biological experiments, confronted with 

 the condition that one and the same discovery may be used, to support 

 entirely opposing views. The old experience of physicians, that iron pills 

 combat chlorosis, can be explained by the assumption that the iron in the 

 pills goes to form the hemoglobin. On the other hand, judging from 

 analogy with other observations, it is perfectly plausible to assume that 

 the iron in the pills merely has an indirect effect in that it excites those 

 organs which take part in the formation of blood into increased activity. 

 First of all, it is necessary to determine whether chlorosis is actually 

 caused by a deficiency of iron. 



Let us see how much iron there is in the human organism. A mouse 

 contains 100 milligrams iron per kilogram of its weight, a guinea pig con- 

 tains but 52 milligrams per kilogram, and a rabbit about 46 milligrams. 

 If we assume that the last value is about right for a human being, then we 

 would have in a person weighing 70 kilograms about 3.2 grams of iron. 

 The question is How much iron does the human organism eliminate? Star- 



