484 X. BILE PIGMENT FORMATION, ETC. 



ing fraction forms only a small part of it, the results are not significant. The 

 subject will be discussed further in Chapter XI. 



5.2. Nonhemoglobin Iron 



If a bile pigment precursor with easily detachable iron exists in the red 

 cells, their total iron content must be higher than their hemoglobin iron 

 content. It might be expected that this difference should be easily 

 established, but this is not so, as the widely different results of such 

 investigations show. 



First, the iron content of hemoglobin itself can only be considered as 

 established within a possible error of±l%. The method used for the 

 estimation of hemoglobin may include other substances, as would, for example, 

 the acid hematin method or the estimation of the carbon monoxide capacity 

 in the presence of dithionite. Choleglobin would be at least partially included 

 in the hemoglobin value determined by the first, and fully in that by the 

 second, method. On the other hand, estimation by oxygen capacity or 

 carbon monoxide capacity without reduction does not include hem/globin. 

 A comparison of the values for nonhemoglobin iron obtained by these different 

 methods by different workers reveals greater differences between the results 

 obtained by different investigators than between those obtained by different 

 methods. Great accuracy of both total iron and hemoglobin estimations is 

 necessary if the small difference is to be significant; it is doubtful whether 

 this accuracy has been achieved in the hands of the investigators concerned 

 (cf. 1431,1435). Peters, working in Barcroft's laboratory, found a difference 

 of 2.5% {2142) between the iron content of erythrocytes and their oxygen 

 capacity, while Barcroft and Burn {lIi-5) found none {cf. 1^1). Of later 

 studies one group of workers finds nonhemoglobin iron to form 6-8% of the 

 total iron {1417,1812), sometimes even more {2184) '- others find no difference, 

 or even less iron than corresponds to the hemoglobin(!) {1081,1235,2005, 

 2589,3013) ; and a third group finds intermediate values, mostly of the order 

 of about 2-3% {136,383,994,995,1811) ; the last values appear to be the most 

 trustworthy ones. Gibson and Harrison {99.5) recently found a difference 

 of 2.0% between total iron and iron calculated from oxygen capacity in 

 human blood; of this difference only 0.6% was due to hem/globin. The 

 remaining 1.4% may be due to choleglobin. 



Some of these investigations have been carried out with the blood of 

 species such as the horse, the blood of which may contain more hem/globin 

 than that of man. Different values have, however, also been found by 

 different investigators in one and the same species, or by methods in which 

 hem/globin would be measured as hemoglobin. 



Bell and co-workers {200) and Macfarlane and O'Brien {1811) have 

 observed that men's blood has slightly, but significantly, higher nonhemo- 

 globin iron than women's blood; this was not confirmed by Gibson and 

 Harrison (.9.9-5). Josephs {1431,1435) found nonhemoglobin iron in the blood 

 of the newborn. The latter observation may explain the findings of Lemberg 

 and co-workers {1704) who ol)tained a rather high biliverdin yield from the 

 erythrocytes of a newborn with icterus gravis neonatorum; the etiology of 



