528 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



and this is believed to be true of all protoplasm. Iron is found through- 

 out the body, and is especially an ingredient of haemoglobin (0.4 per cent.), 

 which carries oxygen to the tissues. It is found deposited in the liver and 

 the spleen as fcrratin. hepatin, and other less investigated organic compounds. 

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

 in all cases, ferric salts arc reduced to ferrous: 



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



Ferric chloride. 



Ferric Phosphate, FeP() 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. 



Ikon ix 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. 5 Feeding 

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

 led 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 ami 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. < hi feeding a dog for thirteen days with meat containing 0. Isu gram Fe, 

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

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

 0.636 gram Fe, and of this 0.6084 gram were recovered in the excreta. 6 This experiment 

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

 tion. Alter eating hi 1 the feces are found to contain much hiematin. and it has been 



thought that iron could not be absorbed in that way. hut Abderhalden 8 has recently shown 

 that there can he a small amount of iron absorption after feeding either haemoglobin or 

 h;ematin. Bunge ha- sought for one of the antecedents of haemoglobin in egg-yolk, 

 and ha> described it as an iron-containing nucleo-albumin, which he names haematogen. 

 That and similar aucleo-albumins existing in plants he conceives to he 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). Small 

 amounts of absorbable iron are found in all the ordinary cereal foods. 7 .Marion" has 



' Macallum : Journal of Physiology, 1894. vol. 1.5, p. 268. 



2 Forster: Zetochrifl fur Bioloijie, 1873, Bd. 9, S. 297. 3 Lor. cit. 



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

 Hermann* Handbook, 1881, vi. 1, S. 385. 



5 Hamburger: Zeitschrifl fur physiologische Chemie, 1878, Bd. 2, S. 191. 



f ' Zeitschrifl fur Biohgie, 1900, Bd. 39, S. 487. 



7 Bunge: Zeitschrifl j'iir ph>i.<ioo>t/i.<rhc <%-mi,\ ls;)s, p„j. 25, S. 36. 



h Archivfiir exper. Pathologic und Pharmakologie, 1891, Bd. 29, S. 212. 



