244 HEMOGLOBIN. 
The Albuminous Eesidue of the Blood-Colouring Matter. 
An unfortunate error has become popular, and has, indeed, been 
propagated by a large number of text-books, namely, that when oxy- 
hemoglobin is decomposed, it splits up into hematin and a definite 
albuminous matter belonging to the group of globulins, and designated 
globin. There is absolutely no ground for such a statement. The term 
globin was, it is true, assigned by Preyer to an albuminous substance, 
which he obtained as a product of the spontaneous decomposition of 
solutions of oxyhemoglobin, but this body did not possess the character- 
istic properties of the globulins, and there is no ground for considering 
it as representing the albuminous body which, by linking to itself a 
coloured iron-containing radicle, forms crystalline haemoglobin. 
Our knowledge on this matter is indeed of the most unsatisfactory 
character. We know, and have shown (see p. 207), that solutions of oxy- 
hemoglobin in the presence of many of the reagents for albumin (so long 
as these do not decompose the blood-colouring matter) behave quite differ- 
ently from solutions of the native albumins, globulins, etc. Thus copper 
sulphate, mercuric chloride, silver nitrate, and the acetates of lead do 
not produce even a cloudiness when added to solutions of pure haemo- 
globin, so long as this remains undecomposed. It has long been recog- 
nised, too, that Lehmann's hypothesis, that the blood-colouring matter 
was composed of colourless crystals tinted by a red pigment, was false ; 
but as to the true nature of the albuminous residue, we have very little 
knowledge, though the facts in our possession almost force us to the 
conclusion that it is not identical in all animals, as shown by the 
difference in the percentage of sulphur in the hemoglobin of the horse 
and the dog. 
The reagents which we employ to decompose the blood-colouring 
matter yield us derivatives of the albuminous residue, not the body 
itself ; we obtain acid albumin as a result of treatment with acids, alkaline 
albuminates as a result of treatment with alkalies. The most interest- 
ing observations on the albuminous products of the decomposition of oxy- 
hemoglobin were published by Kiihne 1 thirty years ago. He showed that 
when C0 2 is passed through solutions of pure oxyhemoglobin a flocculent 
precipitate is thrown down, which does not possess, as had been errone- 
ously asserted by A. Schmidt, fibrinoplastic properties, and which does 
not behave as a globulin. According to Kiihne, this precipitate possesses 
so peculiar an appearance under the microscope that it cannot be mis- 
taken for any other substance. It forms long colourless fibres which 
are so like fibres of connective tissue that they might be taken for them. 
This substance differs fundamentally from globulin ; it is, for example, 
insoluble in water containing oxygen in solution. 
Metilemoglobin. 
Hoppe-Seyler was the first 2 to observe that solutions of oxyhemo- 
globin exposed to the air, or filter papers saturated with such solutions, 
often assume a brown colour. Under these circumstances, the solution 
1 "Lehrbuch," 1866, S. 206, 207. 
2 Centralhl. f. d. med. Wissensch., Berlin, 1864, No. 53. See also Med.-chem. Untcr- 
such., Berlin, S. 378. mid " Die Znsammensetzung des Methamoglobin, nnd seine Umwand- 
lung zu Oxyhemoglobin, " Ztschr. f. physiol. Cliem., Strassburg, 187S, Bd. ii. S. 150, 155. 
