INORGANIC FOODS. 387 



acid the iron is split off and the hematin is changed into hematoporphyrin. 

 The assimilation of the iron, therefore, cannot be a very simple process, 

 and consequently at the time when it was denied that the animal cells 

 possessed the power of effecting syntheses, it is inconceivable why the 

 assumption should, nevertheless, have been made that inorganic iron as 

 such took part in the formation of hemoglobin. This standpoint was 

 emphasized by G. von Bunge, 1 who raised the question as to the form in 

 which the iron is contained in our food supply. Is it present in the 

 form of simple inorganic iron salts, or as complicated organic compounds? 

 He prepared first of all from the yolk of eggs, which must of course 

 contain the iron necessary for the formation of hemoglobin in the blood 

 of the chick, a compound which by its entire chemical behavior was 

 shown to contain iron in a very firm state of combination. 2 On extract- 

 ing the yolk of a hen's egg with alcohol and ether, none of the iron 

 goes into the extract. All of it remains in the residue, which consists 

 chiefly of albumin and nucleins. From this residue the iron cannot be 

 extracted by means of alcohol and hydrochloric acid. Since all salt- 

 like compounds containing iron combined with inorganic or organic acids 

 can be removed by the above reagents, it is to be assumed that the iron 

 is held in a closer form of combination than is the case with its ordinary 

 salts. Bunge next isolated the compound containing iron which was 

 formed by the action of the juices of the stomach during the digestion 

 of protein. The part containing iron does not go into solution. It is 

 indigestible, and corresponds in its entire behavior to that of a nuclein 

 substance. The iron cannot be extracted by alcohol containing hydro- 

 chloric acid, but is dissolved out by aqueous hydrochloric acid, the rate 

 of solution increasing with the concentration of the acid. Although the 

 iron contained in hematin does not react with the ordinary reagents used 

 for detecting the presence of iron, namely, ammonium sulphide, and acid 

 solutions of potassium ferro- and ferricyanides, the iron contained in the 

 nuclein substance does give these tests. By dissolving the nuclein in 

 ammonia, and then adding potassium ferrocyanide and acidifying with 

 hydrochloric acid, a white precipitate is produced which turns blue on 

 standing. In the case of potassium ferricyanide the precipitate remains 

 white. On adding ammonium sulphide to the ammoniacal solution of 

 the nuclein a green coloration is formed, gradually turning black in the 

 course of twelve hours. Recently this compound, to which Bunge gave 

 the name hematogen, has been prepared by Hugonnenq and Morel, 3 and 

 purified from albumin as much as possible. On analyzing it they obtained 



1 Verhandl. des 13. Kongresses fur innere Medizin, p. 133 (1895). 



2 Z. physiol. Chem. 9, 49 (1884). 



3 Compt. rend. 140, 1065 (1905). 



