CRYSTALLINE FORM OF HEMOGLOBIN. 203 



empirical formulae, that calculated by Jaquet for the haemoglobin of the 

 dog is probably the nearest the truth, namely 



Why should haemoglobin possess so enormously high a molecular 

 weight ? The question suggested itself to the acute mind of Bunge, who 

 has furnished us with one reason which is eminently suggestive : " The 

 enormous size of the haemoglobin molecule," says this writer, " finds a 

 teleological explanation, if we consider that iron is eight times as heavy 

 as water. A compound of iron, which would float easily along with the 

 blood current through the vessels, could only be secured by the iron 

 being taken up by so large an organic molecule." 2 



When discussing the compounds and products of decomposition of 

 oxyhaeinoglobin and haemoglobin, we shall have again to revert to and 

 further examine certain of the facts which have found a place in this 

 section. 



The crystalline form, the amount of water of crystallisation, the 

 solubility, and the diffusibility of oxyhsemoglobin. Although, as has 

 already been stated, the oxyhaemoglobin of different animals varies con- 

 siderably in the facility with which it crystallises, we now know that the 

 haemoglobin of all animals, without exception, may, by suitable treat- 

 ment, be obtained in the crystalline form. 3 Great differences exist in 

 the solubility of the blood-colouring matter obtained from different 

 animals, and, as might have been anticipated, the- blood of these 

 animals whose haemoglobin is least soluble (as the rat, the guinea-pig, 

 and the squirrel) yields crystals of oxyhaemoglobin most readily ; whilst 

 the converse is also true, i.e. the oxyhaemoglobin of man, of the rabbit, 

 the sheep, and the ox, all of which are exceedingly soluble, yield crystals 

 with considerable difficulty. It was, indeed, long supposed to be impos- 

 sible to obtain large quantities of oxyhaemoglobin from the blood of 

 certain of these animals. 



As a rule, crystals of oxyhaemoglobin are of such a size that their 

 form, and even their crystalline nature, cannot be made out by the 

 naked eye. The blood of certain animals, however, as the dog, and 

 particularly the horse, yields under favourable circumstances rhombic 

 prisms of macroscopic size. From horse's blood Hoppe-Seyler frequently 

 obtained prisms over 5 mm. in length and 4 mm. in thickness. The 

 colour of crystals of oxyhaemoglobin appears different, according to 

 their size or the number aggregated together. 4 Thus the finest needles 

 or prisms of oxyhaemoglobin, when seen singly under the microscope, 

 appear almost colourless, or possess the yellowish tint characteristic of 

 the coloured corpuscles. On the other hand, large crystals, or consider- 



1 From the results of Hiifner's analyses of the haemoglobin of the ox, but substituting 

 his most recent determinations (1894) of the iron for the older ones, published in 1887, I 

 have calculated for the haemoglobin of this animal the formula 



C 759 H 1208 N 210 S 2 Fe0 204 



2 G. Bunge, "Text-Book of Physiological and Pathological Chemistry." Translated by 

 L. G. Wooldridge : London, 1890, p. 24. 



3 It was Dr. Otto Funke who first asserted, as the result of his own researches, " that 

 all blood is capable of crystallisation, whatever animal or organ it may be taken from."- 

 " Explanation of the Plates" of his "Atlas of Physiological Chemistry," p. 15 (see p. 205, 

 note 1). 



4 F. Hoppe-Seyler, "Das Oxyhamoglobin des Pferdeblutes," Ztsclir. f. physiol, Chcm., 

 Strassburg, 1878-79, Bd, ii, S, 149. 



