190 HAEMOGLOBIN, 



Hypothesis of Hoppe-Seyler, that the coloured substance of the 

 corpuscles possesses properties which differ from those of hsemo- 

 globin Arterin (?), and Phlebin (?). It has been shown that we are 

 forced to assume the existence in the coloured corpuscles of a very unstable 

 compound of haemoglobin. Hoppe-Seyler, as far back as 1877, 1 expressed the 

 opinion that whilst the compound or compounds of haemoglobin existing in the 

 blood corpuscles absorb the rays of the spectrum precisely as solutions of 

 haemoglobin, in other respects very remarkable differences can be detected, 

 certain of these differences being, in his opinion, of great physiological 

 importance. 



Subsequently, 2 Hoppe-Seyler, returning to this subject, endeavoured to 

 prove by a variety of arguments that such are the differences between the 

 properties of the colouring matter as it exists in the coloured corpuscles and 

 pure haemoglobin, that we cannot logically assert that they are identical. He 

 examined in detail the differences in behaviour which had been observed by 

 himself and by others, between the blood-colouring matter as it exists in the 

 corpuscles and solutions of pure oxy- or reduced haemoglobin. He referred to 

 the undoubted fact that the colouring matter, as it exists in the coloured 

 corpuscles, is not dissolved out by serum, liquor sanguinis, or saline solutions, 

 of a certain strength. It does not, he alleged, crystallise, nor readily yield 

 its dissociable oxygen when heated in vacua it readily decomposes peroxide 

 of hydrogen (H 2 2 ), setting free ordinary inactive oxygen, and is not oxidised 

 during the process ; a solution of potassium ferricyanide does not for a long 

 time attack the blood corpuscles, or convert their colouring matter into 

 methsemoglobin. 



On the other hand, a solution of oxyhaemoglobin (or, as Hoppe-Seyler 

 preferred to express it, of the oxyhcemoglobins, so as to recall the fact of the 

 minor differences presented by the haemoglobin of different species of animals) 

 is soluble in serum or in blood plasma, or in solutions of the neutral salts ; 

 it crystallises with greater or less facility, according to the animal whence 

 the blood is obtained. When thoroughly pure, it has scarcely any power 

 of decomposing H 2 9 , but under the influence of this body it is readily 

 oxidised. 



Solutions of crystallised oxyhaemoglobin, Hoppe-Seyler maintained, give 

 up their dissociable oxygen with difficulty and incompletely, when heated 

 in vacuo. When blood is saturated with CO, this gas can subsequently be 

 entirely removed, by passing a stream of hydrogen gas through it for some 

 hours, or by long-continued boiling in vacuo. On the other hand, when a 

 solution of oxyhaemoglobin is saturated with CO, and the solution is heated 

 in vacuo, the poisonous gas is, Hoppe-Seyler stated, given off with great 

 difficulty and incompletely. 



Lastly, highly dilute solutions of potassium ferricyanide readily convert the 

 oxyhaemoglobins into methaemoglobin. 



The evidence by which Hoppe-Seyler endeavoured to prove that the 

 properties of the blood-colouring matter, as it exists in the corpuscles, differ so 

 greatly from those of haemoglobin, that we cannot with truth say that this 

 body exists in them, is, on every single point, of so unsatisfactory a character 

 as not to stand a moment's investigation, and would lead us to reject his 

 hypothesis, even if we had not been placed in possession of some remarkable 

 facts bearing on this subject, which have been ascertained by the method of 

 spectrophotometry. The non-crystallisation of the colouring matter as it 

 exists in the coloured corpuscles might, were it really true, well be explained 

 by the fact that haemoglobin does not exist in a free state, but is combined 



1 " Physiologische Chemie," Berlin, 1877, Th. 1, S. 381. 



2 "Beitrage zur Kenntniss des Blutfarbstoffes," Ztschr. f. physiol, Chem., Strassburg, 

 1889, Bd. xii'i. S. 477. 



