74 PHYSIOLOGICAL CHEMISTRY. 



Nitric -oxide Haemoglobin is also a crystalline molecular com- 

 bination which is even stronger than the carbon-monoxide haemo- 

 globin. Its solution shows two absorption-bands which are paler 

 and less sharp than the carbon-monoxide haemoglobin bands, and 

 they disappear on the addition of reducing bodies. 



Haemoglobin forms also a molecular combination with acetylene. It is also 

 claimed that it forms a combination with hydrocyanic acid. 



Carbon - dioxide Haemoglobin. Haemoglobin forms a molecular 

 combination with carbon dioxide whose spectrum is similar to that 

 of haemoglobin (ToRtip). By the action of carbon dioxide on 

 haemoglobin part of the latter is decomposed with the separation of 

 albumin (BoHR, TORUP), and the combination seems to be rather 

 carbon-dioxide haemochromogen (see below : Hasmochromogen). 



Methaemoglobin. This name has been given to a coloring matter 

 which is easily obtained from the oxyhaemoglobin as a transforma- 

 tion product and which has been correspondingly found in transuda- 

 tions and cystin fluids containing blood, in urine, in haematuria or 

 haemoglobinuria, also in urine and blood on poisoning with potas- 

 sium chlorate, amyl nitrite or alkali nitrite, and many other 

 bodies. 



Methaemoglobin does not contain any oxygen in molecular or 

 dissociable combination, but still the oxygen seems to be of im- 

 portance in the formation of methaemoglobin. If arterial blood be 

 sealed up in a tube, it gradually consumes its oxygen and becomes 

 venous, and by this absorption of oxygen a little methaemoglobin is 

 formed. The same occurs on the addition of a small quantity of 

 acid to the blood. By the spontaneous decomposition of blood 

 some methaemoglobin is formed, and by the action of ozone, potas- 

 sium permanganate, potassium ferricyanide, and certain other 

 bodies on the blood an abundant formation of methaemoglobin 

 takes place. 



According to a few investigators, among others SORBY and 

 JADERHOLM, the methaemoglobin contains more oxygen than 

 oxyhaemoglobin, while according to others, among whom may be 

 mentioned HOPPE-SEYLER, it contains less. HUFNER and OTTO 

 claim that it contains just as much oxygen, but that it is more 

 strongly combined. JADERHOLM and SAARBACH claim that a 



