280 THE BLOOD. 



Carbon-dioxide Haemoglobin, Carbohcemoglobin. Haemoglobin, accord- 

 ing to BOHR and ToRUP, 1 also forms a molecular combination with car- 

 bon dioxide whose spectrum is similar to that of haemoglobin. Accord- 

 ing to BOHR there are three different carbohaemoglobins, namely, a-, 

 /?-, and 7--carbohaemoglobin, in which 1 gram combines with respectively 

 1.5, 3, and 6 cc. CO 2 (measured at C. and 760 mm.) at 18 C. and a, 

 pressure of 60 mm. mercury. If a haemoglobin solution is shaken with a 

 mixture of oxygen and carbon dioxide, the haemoglobin combines loosely 

 with the oxygen as well as with the carbon dioxide, independently of 

 each other, just as if each gas existed alone (BOHR). He considers 

 that the two gases are combined with different parts of the haemoglobin, 

 that is, the oxygen with the pigment nucleus and the carbon dioxide 

 with the protein component. BOHR has given an equilibrium formula 

 for the carbon-dioxide absorption of haemoglobin at different carbon- 

 dioxide tensions, and the results obtained on calculation, using this for- 

 mula, correspond very well with the results obtained directly. Attention 

 must be called to the fact that, as observed by TORUP, haemoglobin is 

 in part readily decomposed by the carbon dioxide with the splitting off 

 of some protein. 



Nitric -oxide Haemoglobin is also a crystalline molecular combina- 

 tion which is even stronger than the carbon-monoxide haemoglobin. 

 Its solution shows two absorption-bands, which are paler and less sharp 

 than the carbon-monoxide haemoglobin bands, and they do not disappear 

 on the addition of reducing bodies. Haemoglobin also forms a molecular 

 combination with acetylene. 



Hsemorrhodin is the name given by LEHMANN to a beautiful red pigment 

 soluble in alcohol and ether, which is extracted from meat and meat products 

 by boiling alcohol and which seems to be produced by the action of small amounts- 

 of nitrites. Another pigment isolated by LEWIN 2 from the blood of animals- 

 poisoned by phenylhydrazine, has been called hcemoverdin. By heating a solu- 

 tion of blood-pigment treated with caustic potash and mixed with alcohol ta 

 60 C. we obtain, according to v. KLAVEREN, a pigment which he calls kathoemo- 

 ylobin, but called by ARNOLD,* who first obtained it, neutral hoematin, which is 

 produced by the splitting off of a ferruginous complex. This pigment still con- 

 tains protein, but is poorer in iron than the hemoglobin or methsemoglobin and 

 probably forms an intermediary product in the conversion of the above into 

 hspmatin. 



Decomposition products of the blood-pigments. By its decomposi- 

 tion haemoglobin yields, as previously stated, a protein, which has been 



1 Bohr, Extrait du Bull, de 1'Acad. Danoise, 1890; Centralbl. f. Physiol., 4 and 

 17; Torup, Maly's Jahresber., 17. 



2 K. B. Lehmann, Sitzungsber. d. phys.-med. Gesellsch. Wurzburg, 1899; Lewin,. 

 Compt. rend., 133. 



3 v. Klaveren, Zeitschr. f. physiol. Chem., 33; Arnold, ibid., 29. 



