222 CARBON-MONOXIDE HEMOGLOBIN. 



tions of haemoglobin exist which, while they cannot be discriminated 

 by their purely chemical characteristics, exhibit a marked difference as 

 to the amount of oxygen with which the same quantity of each can 

 unite under similar external conditions ; the results thus obtained are 

 stated to hold good for the compound of oxygen with haemoglobin as it 

 exists in the red blood-corpuscles of the dog 1 , and further for the 

 haemoglobin of guinea-pigs and geese 2 . Further investigation must 

 decide the interesting questions raised by the above statements. 



There appears to be a consensus of opinion that haemoglobin, and 

 more particularly oxy-haemoglobin, possesses to a slight degree the 

 properties of an acid. This view appears to be based on the following 

 facts. Oxy-haemoglobin is extraordinarily soluble in alkalis and in 

 this solution appears to be more stable than ordinarily. It is further 

 stated that it has a feeble power of facilitating the evolution of carbon- 

 dioxide from dilute solutions of sodium carbonate 3 . It is hence often 

 supposed that in the red blood-corpuscles the haemoglobin is united to 

 the alkalis of which their stroma partially consists. If the above 

 views are correct they may assist in explaining to some slight extent 

 the difficulties in understanding the causes of the exit of carbon- 

 dioxide from venous blood during its passage through the lungs. 

 (See 357.) But the possibility here indicated must be received with 

 the greatest caution ; for it has been shown that although a dilute 

 alkaline solution of oxy-haemoglobin when exposed to a low partial 

 pressure of carbon-dioxide absorbs less of this gas than suffices to 

 convert the alkali into bicarbonate, thus acting like an acid, at higher 

 partial pressures it absorbs more than can be accounted for by the 

 change of the alkali into bicarbonate. In the latter case the haemo- 

 globin seems to act like a feeble base 4 . It is interesting here to 

 notice that if the immediately preceding statements hold good, the 

 haemoglobin must possess increasingly acid properties in proportion 

 as the carbon-dioxide begins to be evolved from the blood, and might 

 thus further that exit. The power apparently possessed by haemoglobin 

 of itself uniting directly with carbon-dioxide will be referred to again 

 later on. 



3. Carbon-monoxide haemoglobin. When a current of car- 

 bon-monoxide is passed through a solution of oxy-haemoglobin the oxygen 

 is driven off and its place taken by the first-named gas. The compound 



1 Bohr u. Torup, Slcandinav. Arch. f. Physiol. Bd. in. Hft. 1, 2 (1891), S. 69. 

 Bohr, Ibid. Sn. 76, 101. 



2 Jolin, Arch. f. Physiol. Jahrg. 1889, S. 265. 



3 Preyer, Die Blutkrystalle, 1871, S. 70. 



4 Setschenow, Mem. de I'Acad. de St Petersb. T. xxvi. 1879, confirmed by 

 Zuntz, Hermann's Hdbch. d. Physiol. Bd. iv. Th. 2 (1882), S. 76. 



