INORGANIC FOODS. 395 



A second method * for deciding the question concerning the assimila- 

 tion of iron is to withdraw equal quantities of blood from two animals of 

 the same age and, as far as possible, of the same condition of nourishment, 

 and then to compare the regeneration of blood in one case where the 

 animal is fed entirely upon milk, and in another where iron is added to the 

 milk. Here all authors agree that the animal to which the inorganic 

 iron has been fed is able to replace the lost blood much more quickly 

 than the other animal to which only the iron contained in milk is avail- 

 able. The disagreement in this result with that obtained in above experi- 

 ments may perhaps be due to the different conditions of the animals in 

 the two types of experiments. In the first instance, animals were chosen 

 whose iron stores at the beginning of the experiment were in a quite 

 exhausted state. All of the iron in the different tissues was brought 

 down to the lowest limit. The animals in the second cases were in an 

 entirely different condition. These possessed a considerable supply of 

 stored-up iron, and would have been able to supply the loss in hemoglo- 

 bin iron from these stores alone. That the addition of inorganic iron 

 exerts a favorable action might be in fact explained on the assumption 

 that it excites the action of the blood-forming organs. We must admit, 

 however, that such an explanation does not seem well founded in this 

 case, for it would seem probable the large loss of blood would of itself 

 serve to incite the organs which take part in the formation of blood into 

 increased activity. On the other hand, it is conceivable that the inorganic 

 iron replaces the iron in the tissues, so that the latter is left free to take 

 part in the formation of hemoglobin. No one has ever been able to prove 

 this directly, but it seems to be a likely explanation, as we shall see from 

 what follows. 



Franz Miiller 2 hoped to settle this question by an examination of 

 bone-marrow, one of the principal places where the red blood-corpuscles 

 are formed. Miiller fed dogs, taken immediately upon the completion of 

 the lactation period, on the one hand exclusively with milk, and on the 

 other with milk and iron. After subsequently killing the animals, he 

 found that the bone-marrow of the animals fed with iron contained con- 

 siderably more nucleated, red blood-corpuscles than the animals fed 

 with milk alone. Again, this discovery may be interpreted in two differ- 

 ent ways. We may assume that the inorganic iron takes part directly 

 in the formation of hemoglobin, or, on the contrary, that it merely exerts 

 an indirect action. 



When we take into consideration all of the different experiments that 

 have been performed in this connection, we must unhesitatingly admit 

 that it has never been satisfactorily proved whether the iron taken into 



1 Kunkel: Pfliiger's Arch. 61, 596 (1895). Eger: Z. klin. Med. 22, 335 (1897). 

 3 Loc. cit. Cf. also A. Hofmann: loc. cit. 



