CRYSTALLINE FORM OF HEMOGLOBIN. 203 
empirical formulae, thai calculated by Jaquet for the haemoglobin of the 
dog is probably the nearest the truth, namely — 
C 768 ] I ,,„;, N^S, FeO, 18 1 
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 he secured by the iron 
being taken up by so large an organic molecule." 2 
When discussing the compounds and products of decomposition of 
oxyhemoglobin 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 oxyhaemoglobin. — Although, as has 
already been stated, the oxyhemoglobin 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 oxyhemoglobin most readily ; whilst 
the converse is also true, i.e. the oxyhemoglobin 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 oxyhemoglobin from the blood of 
certain of these animals. 
As a rule, crystals of oxyhemoglobin 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. 1 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, hut substituting 
his most recent determinations (1S94) of the iron for the older ones, published in 1S87, I 
have calculated for the haemoglobin of this animal the formula — 
^7 5 3 r ^12O8-"210' , 2-' e '-'i0 4 
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 Oxyhemoglobin des Pferdehlutes," Ztschr. f. physiol. Chem., 
Strassburg, 1878-79, Bd. ii. S. 149, 
