26 DISTRIBUTION OF HEMOGLOBIN AND ALLIED SUBSTANCES 



cor 



^respond to 1 atom of iron. The figures so far only demonstrate that there is at least 

 four times as much oxygen taken up in the transition of hemoglobin into oxyhemoglobin 

 as there is in the transition from suboxid to oxid of iron, or from ferrocyanid to ferri- 

 cyanid of potassium. Possibly the sulphur of the hemoglobin also plays a part in the 

 loose oxygen compound, and a similar part may be assigned to the sulphur atoms in all 

 proteins. It is noteworthy that, according to previous analyses, the animals that require 

 more oxygen have likewise more sulphur in their hemoglobin. 



That the protein is really an active factor in relation to the displace- 

 able or respiratory oxygen has, for instance, been clearly indicated by the 

 differences in the behavior of hemoglobin when in the erythrocyte and 

 after removal from it, and by the recent researches of Ham and Balean 

 (Journal of Physiology, 1905, xxxn, 312), who write that- 



It would appear that one of the oxygen atoms in oxyhemoglobin is differently 

 combined to the other, i.e., it is more intimately attached to the iron, and further that 

 hematin still contains oxygen linked to the iron, only half being displaced in its forma- 

 tion from oxyhemoglobin by the action of dilute acids. This we should expect, from 

 the fact that it requires a strong acid to form hematoporphyrin not only from oxyhem- 

 oglobin but also from hematin, whereas a weak acid readily effects the change in the 

 case of reduced hemoglobin (Laidlaw). The reason for this is supposed to be that iron 

 linked to oxygen is more stable than iron not so linked; in other words, the presence of 

 oxygen attached to iron much increases the difficulty that acids have in removing the 

 iron and forming hematoporphyrin. Again, since one oxygen atom, and not both, is 

 displaced by the action of dilute acids on oxyhemoglobin in the formation of acid 

 hematin, we are justified in supposing that the particular oxygen atom which is disso- 

 ciated is not linked to iron in the same way as the one which is not displaced. Now 

 the effect of dilute acids on oxyhemoglobin is not only to set free one oxygen atom, 

 but also to split off the globin radicle. And we have found from experiment that as 

 more and more oxygen is liberated so more and more acid hematin is formed, and there- 

 fore more and more globin is split off. But further than this, when we have displaced 

 half of the replaceable oxygen we find nothing but acid hematin, and therefore all the 

 globin must have been dissociated from the oxyhemoglobin molecule. It therefore ap- 

 pears that this displaced oxygen atom must bear some definite relation to the globin 

 radicle, the other oxygen atom having both its oxygen affinities satisfied by the iron. 



The further action of the acid is then to split the bond between the oxygen atom 

 and the globin radicle. 



The absorptive power of erythrocytes as regards O is accredited to the 

 hemoglobin, and as regards C0 2 to the alkali of the phosphates and globulin 

 and to hemoglobin. The combination of CO 2 with hemoglobin does not 

 give a compound that is to be classed with CO-hemoglobin and 0-hemo- 

 globin, because the CO 2 and are not interchangeable in the quantitative 

 relationship that is observed with CO and O. Bohr and his co-workers 

 (Bohr, Festschrift f. C. Ludwig, 1887, 164; Compt. rend. soc. biolog., 1891, 

 cxi, 243; Zentralbl. f. Physiologic, 1904, xvn, 688, 713; Jolin, Archiv f. 

 Aunt. u. Physiologie, 1891, m, 69; Torup, Biochem. Centralbl., 1906, v, 667; 

 Maly's Jahr. ii. d. Fort. d. Thierchemie, 1906, xxxvi, 166) have recorded 

 that the CO 2 -capacity of hemoglobin is markedly higher than for (which 

 property has been found by Griffiths to be shown by the achroglobulins) ; 

 that the C0 2 -capacity is relatively high at low pressures and low at high 

 pressures; that C0 2 is more readily dissociated than 0; that the 0-capacity 

 of the blood may be decidedly affected by changes in the tension of C0 2 , 



