276 THE BLOOD.. 



Pseudohaemoglobin. LUDWIG and SIEGFRIED l have observed that blood 

 which has been reduced by hyposulphites so completely that the oxy haemoglobin 

 spectrum disappears and only the haemoglobin spectrum is seen, yields large 

 amounts of oxygen when exposed to a vacuum. Blood which has been reduced 

 by the passage of a stream of hydrogen through it until the oxyhaemoglobin 

 spectrum disappears acts in the same manner. Hence a loose combination of 

 haemoglobin and oxygen exists which gives the haemoglobin spectrum, and this 

 combination is called pseudohaemoglobin by LUDWIG and SIEGFRIED. Pseudo- 

 haemoglobin, whose presence has been detected in asphyxiation "blood from dogs, 

 is considered by HAMMARSTEN as an intermediate step between haemoglobin and 

 oxyhaemoglobin on the reduction of the latter. The occurrence of pseudohaemo- 

 globin does not seem to have been positively proven. 2 



Methaemoglobin. This name has been given to a coloring-matter 

 which is easily obtained from oxyhsemoglobin as a transformation product 

 and which has been correspondingly found in transudates and cystic 

 fluids containing blood, in urine in hsematuria or hsemoglobinuria, and 

 also in urine and blood on poisoning with potassium chlorate, amyl 

 nitrite or alkali nitrite, and many other bodies. 



Methsemoglobin does not contain any oxygen in molecular or dis- 

 sociable combination, but still the oxygen seems to be of importance in 

 the formation of methsemoglobin, because it is formed from oxyhsemo- 

 globin and not from haemoglobin in the absence of oxygen or oxidizing 

 agents. 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 

 methsemoglobin is formed. The same occurs on the addition of a sir all 

 quantity of acid to the blood. By the spontaneous decomposition of 

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

 sium permanganate, potassium ferricyanide, chlorates, nitrites, nitro- 

 benzene, pyrogallol, pyrocatechin, acetanilide, and certain other bodies 

 on the blood an abundant formation of methsemoglobin takes 

 place. 



According to the investigations of HUFNER, KULZ, and OTTO 3 

 methsemoglobin contains just as much oxygen as oxyhsBmoglobin, but 

 it is more strongly combined. By the action of potassium ferricyanide 

 or potassium permanganate upon oxyhsemoglobin first 1 molecule oxygen 

 (i.e., the entire quantity of loosely combined oxygen) is split off, and in 

 the subsequent methsemoglobin formation either two oxygen atoms 

 (HALDANE) or two hydroxyl groups are combined (HUFNER, v. ZEYNEK 4 ). 

 Methsemoglobin solutions are reduced to hemoglobin by reducing agents. 

 JADERHOLM and SAARBACH claim that methsemoglobin is first converted 



1 Arch. f. (Anat. u.) Physiol., 1890; see also Ivo Novi, Pfluger's Archiv, 56. 



2 See Hiifner, Arch. f. (Anat. u.) Physiol., 1894, 140. 



3 See Otto Zeitschr. f. physiol. Chem., 7. 



4 Haldane, Journ. of Physiol., 22; v. Zeynek, Arch. f. (Anat. u.) Physiol., 1899; 

 Hiifner, ibid. 



