272 THE BLOOD. 



combines with more oxygen, calculated per 1 gram haemoglobin, than a 

 concentrated solution. BOHR suggested another formula expressing the 

 relationship between the oxygen absorption and the oxygen tension, 

 based upon the assumption that, besides the dissociation of the oxygen- 

 hemoglobin compound, a dissociation of the haemoglobin into a part 

 containing iron and a part containing no iron also takes place. This 

 formula, which in fact accords well with BOHR'S findings, is nevertheless 

 only true for a hemoglobin solution and not for blood, as, according to 

 BOHR, the blood-pigment in the blood-corpuscles (the hemochrom) is 

 changed on being converted into haemoglobin. HENRI 1 also finds that 

 HUFNER'S formula for the dissociation of oxyhemoglobin is not useful. 



The native pigment, the ha?mochrom, combines, according to BOHR, 

 in maximum with the same quantity of oxygen as the corresponding 

 haemoglobin, when the latter is prepared without the use of violent 

 methods; still from this it does not follow that the oxygen combina- 

 tion in hemochrom is identical with that in haemoglobin. According 

 to BOHR this is not the case, at least with diminished pressure, for with 

 low oxygen tension more oxygen is taken up by the blood than by a 

 corresponding hemoglobin solution. The curve showing the oxygen 

 absorption is lower in this case for a haemoglobin solution than for blood. 

 The reason for this lies, according to BOHR, in the fact that the tension 

 curve is influenced by the form of union of the part of the haemoglobin 

 containing iron with the iron-free part, and that this union is changed 

 because of changes in the iron-free part, as by the splitting off of lecithin, 

 etc. The tension curve of the oxygen in the blood can, according to 

 BOHR, be determined only by direct experiments on the blood itself and 

 not by experiments upon hemoglobin solutions. 



The elucidation of these conditions is of the very greatest importance, 

 as the dependence of the reaction between OHb, Hb, and O upon the 

 law of mass-action is naturally of the very greatest moment for the 

 taking up of oxygen in the lungs and the giving up of the same to the 

 tissues. The dissociation of the oxyhemoglobin makes it also possible 

 to completely expel the oxygen from a hemoglobin solution or from 

 blood by means of a vacuum or by passing an indifferent gas through the 

 blood. 



Oxyhemoglobin, which is generally considered as a weak acid, is 

 dextrorotatory, according to GAMGEE. 2 The Specific rotation for light 

 of medium wave-length of C is (a) C = about +10, which corresponds 

 also for carbon-monoxide hemoglobin. The hemoglobin is also, like 

 carbon-monoxide hemoglobin (COHb) and methemoglobin (MHb), 

 diamagnetic, while the hematin, which is richer in iron, is strongly mag- 



1 Henri, Compt. rend. soc. biolog., 56. 2 Hofmeister's Beitrage, 4. 



