470 CHEMISTRY OF THE PROTEIDS CHAP. 



" there is in the haemoglobin of all animals absolute identity of the 

 essential iron-containing nucleus, i.e. of that moiety of the molecule on 

 which its colour and its physiological function depend, that at the same 

 time there is such a difference in the ratio of S : Fe in the haemoglobin 

 of certain animals as renders it highly probable, or rather certain, that 

 in the haemoglobin of different animal groups the albuminous moiety of 

 the complex molecule differs. Such being the case, it is not surprising 

 that certain of the physical characters of haemoglobin, such as crystal- 

 line form and solubility, should exhibit variations," and " that haemo- 

 globins varying in certain physical properties may be formed by the 

 linking of the iron-containing molecule to various polymeric combina- 

 tions of the same albuminous molecule." See also p. 474. 



Gamgee's view seems to the author to be also supported by the fact 

 that the amount of water of crystallisation differs for different animals, 

 amounting to the following percentages : dog, 3 '4 (Hoppe-Seyler) ; 

 horse, 3'94 (Hiifner) ; pig, 5 '9 (Otto); guinea-pig, 6 (Hoppe-Seyler); 

 and squirrel, 9 (Hoppe-Seyler). 1 In further support may be mentioned 

 the recent work of Ham and Balean (see p. 507), who have shown that the 

 globin radical of haemoglobin may be replaced by some constituent of 

 egg-white. At present we have no right to suppose that the haematin 

 radical in one and the same animal is always linked to exactly the 

 same albuminous moiety, for there is no a priori reason against the 

 view held by MacMunn that myohaematin differs from blood-haemoglobin. 



To put it shortly : the haematin of all animals is alike, while the 

 albuminous element is not. 



Hoppe-Seyler 2 in 1889 brought forward the view that in living 

 blood special compounds, 'phlebin' and 'arterin,' are present, and 

 that out of them reduced- and oxyhaemoglobin are formed secondarily. 

 Robert 3 has subsequently defended this view, and Bohr 4 distinguishes 

 also between several modifications of oxyhaemoglobin (see p. 494). 



How difficult it is to purify haemoglobin has already been pointed 

 out, as, according to Abderhalden, haemoglobin which was crystallised 

 only once still contained up to 15 per cent of extraneous albumins 

 and the haemoglobin of animals possessing nucleated red blood- 

 corpuscles (birds, reptiles, etc.) contains, even after repeated recry- 

 stallisation, phosphorus derived from the nucleic acid of the compounds 

 of the nucleus. 



1 Gamgee's Table on p. 205 of Schdfers Textbook of Physiology, vol. i. (1898). 



2 F. Hoppe-Seyler, Zeitschr. f. physiol. Chem. 13. 477 (1889). 



3 H. U. Robert, Zeitschr. f. angewandte Mikroskopie, V. 6 to 10 (1900) ; R. Kobert, 

 Deutsche Arztezeitung, 1900, Heft 18. 



4 Bohr, Zentralbl. f. Physiol. 4. 242, 254 (1890), 



