MINERAL METABOLISM 329 



of the colon, perhaps in very small part by way of the bile. That bile 

 may contain iron has long been known, but the figures given show a wide 

 variation which may be ascribed in part to faulty methods of analysis, in 

 part perhaps to a different behavior of various forms of iron (Leone). The 

 clear connection between hemoglobin and the bile pigments and the place of 

 formation of the latter, unquestionably the liver, need not be reviewed 

 here. The iron thus set free is deposited in the organs or gradually elimi- 

 nated, but whether the amount of urobilin in the feces is a reliable index 

 of blood destruction in health and in disease is uncertain (Me Cradden(d) ; 

 Robertson(a) ; Whipple and Hooper(a) ). Bunge's theory of a protective 

 action of iron salts against hydrogen sulphid in the intestine has been 

 discarded because of the proven absence of hydrogen sulphid in the small 

 intestine (Macfayden, Nencki and Sieber). 



The urinary elimination of iron has been the subject of many investi- 

 gations with widely different results (earlier literature cited by Socin) but 

 by the method of Neumann which gave constant results it appeared to be 

 about 1 mg. in 24 hours, perhaps much less (Marriott and Wolf), a small 

 fraction of which is decomposable by (NH 4 ) 2 S and heat, the rest being 

 in complex organic combination, perhaps of the nature of a pigment or 

 of a non-coagulable protein compound (Monier). A small proportion 

 of intravenously or subcutaneously injected iron appears in the urine 

 (Damaskin), most of it, however, is eliminated by way of the intestine 

 (Lipski). The urinary excretion of iron varies in some pathological 

 conditions (the literature is cited by Goodman), but the kidneys play a 

 minor part in the excretion of iron (Fini ; Lapicque; Woltering). 



Experiments on iron metabolism date back as far as 1849 when Ver- 

 deil showed that the ash of dogs fed meat contained more iron than that 

 of dogs given bread (for the early literature see Hall) ; the accumulation 

 of iron in the liver after intravenous injection (Zaleski; Gottlieb(a)) and 

 after ingestion in organic or inorganic form (Kunkel ; Salkowski(c) ; 

 Tartakowsky(fc) ; Oerum(a) ; Bonanni(fc)) especially after the organic 

 (Samoljoff) not only in liver but also in spleen, muscles and bones has 

 been determined repeatedly. The iron-free feeding experiments of v. 

 Hoesslin are the earliest of their kind. By such food and by bleeding he 

 deprived growing dogs of iron ; their hemoglobin fell and anemia was also 

 evident in a paleness of the mucous membranes, but growth was not inter- 

 fered with; similar results were obtained on rabbits. The interesting 

 experiments of Schmidt on mice showed that iron-poor food did not produce 

 anemia or a fall in hemoglobin in full-grown animals but that the offspring 

 of such animals, on the same iron-free food, were retarded in growth am 

 developed severe anemia, with disappearance of iron stores in the liver and 

 their diminution in the spleen. According to Fctzer the administration 

 of iron-poor food to pregnant rabbits and guinea pigs caused a depleti 

 of the iron supplies of the mother up to a certain point, but the maternal 



