972 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



It is found in muscle washed free from blood. Iron appears in urine and in 

 milk as organic compounds, and in the bile, gastric juice, and intestines as 

 phosphate, in the feces as sulphide. Iron occurs in two forms, the ferro- and 

 ferri- compounds, in which it has respectively two and three bonds. 



Ferrosulphide, FeS. This is found in the feces and is the product of 

 the action of sulphuretted hydrogen or alkaline sulphide on both inorganic 

 iron and likewise, more slowly, on organic iron-containing compounds (fer- 

 ratin, haematogen, etc.). Ammonium sulphide acts in a similar manner, and, 

 in all cases, ferric salts are reduced to ferrous : 



2FeCl 3 + 3(NH 4 ) 2 S = 2FeS + 6NH 4 C1 + S. 



Ferric chloride. 



Ferric Phosphate, FePO 4 . This is found in the gastric juice, bile, and 

 probably in the intestinal juice; 1 it is not, as many have believed, given off 

 by the epithelia of the intestines. It is soluble in mineral acids, but insoluble 

 in water, alkalies, or acetic acid. 



Detection. Ammonium sulphide gives a black precipitate of ferrous sulphide in all 

 iron solutions. Ferrocyanide of potassium gives a deep blue coloration (Berlin-blue) to 

 solutions of ferric salt. Ferricyanide of potassium gives Turnbull's blue, very similar 

 to Berlin-blue, with solutions of ferrous salts. 



IKON IN THE BODY. The amount of iron in the urine is very small, 

 amounting daily in a large starving dog to 0.0013-0.0049 gram. 1 Feeding 

 iron compounds does not increase the amount of iron in the urine. Forster 3 

 fed a dog of 26 kilograms for thirty-eight days with washed meat containing 

 0.93 grams of iron, and in the feces were found 3.59 grams belonging to the 

 same period. Here there was a loss of 2.66 grams 4 of iron from the body, 

 and the necessity of iron as a food was established. 



Concerning the method and the amount of iron-absorption, considerable difficulty has 

 been encountered owing to the fact that both absorptive and secretive organs lie in the 

 intestinal canal. On feeding a dog for thirteen days with meat containing 0.180 gram Fe, 

 there were found in urine and feces for the same time 0.1765 gram Fe ; then to the same 

 food for a similar length of time were added 0.441 gram Fe (as sulphate), making in all 

 0.636 gram Fe, and of this 0.6084 gram were recovered in the excreta. 5 This experiment 

 proves only that such absorption as may take place is pretty nearly balanced by the excre- 

 tion. After eating blood the feces are found to contain much haematin, and it is believed 

 that iron cannot be absorbed in that way. Bunge 6 has sought for one of the antecedents 

 of haemoglobin in egg-yolk, and has described it as an iron-containing nucleo-albumin, 

 which he names haematogen. That and similar nucleo-albumins existing in plants he con- 

 ceives to be the source of absorbable iron, while inorganic salts of iron aid only indirectly 

 by forming iron sulphide, thus preventing the same formation from organic iron (see above). 

 Marfori 7 has prepared a substance from proteid and iron salts, called ferratin, which con- 

 tains 4 to 8 per cent, of iron ; it is a compound unaffected by gastric juice or by boiling ; it 



1 Macallum : Journal of Physiology, 1894, vol. 15, p. 268. 



2 Forster: Zeitschrift fur Biologic, 1873, Bd. 9, p. 297. 3 Lor. dt. 



4 This figure is probably too high, but the principle itself is fundamental. See Voit, 

 Hermann's Handbook, 1881, vi. 1, p. 385. 



5 Hamburger: Zeitschrift fur physiologische Chemie, 1878, Bd. 2, p. 191. 



6 Zeitschrift filr physiologische Chemie, 1884, Bd. 9, p. 49. 



T Archiv fiir exper. Pathologic und Pharmakologie, 1891, Bd. 29, p. 212. 



