ELEMENTA R J ' COMPOSITION OF OX YH.EMO GL OB IN. 2 o 1 
Varrentrapp), though the results which he obtained differed in a remarkable 
manner from all those of previous observers. It is cleat that whilst very great 
value must be attached to the determination of the iron and sulphur contained in 
haemoglobin, made by Zinoffsky, his conclusions as to the percentage of carbon 
and hydrogen must be rejected, as being based upon an insufficient number 
1 if analyses, and as being in all probability incorrect. This opinion is supported 
by the remarkable discrepancy between his results and those of other observers 
— a discrepancy which cannot be accounted for by differences in purity of the 
bodies analysed. 
While it is almost inconceivable, and against the weight of evidence, that 
haemoglobin derived from animals of the same species should not have a 
constant composition, the differences in centesimal composition which certainly 
do exist between the haemoglobin of certain animals and that of others 
cannot surprise us when we reflect that haemoglobin does exhibit marked 
physical differences in different animals — that it exhibits variations in 
crystalline form, in the amount of water of crystallisation, and in solubility. 
The study of the general results of the ultimate analyses of oxy- 
hemoglobin made of recent years forces us assuredly to the conclusion 
that new and still more precise investigations are needed before we can 
lay claim even to so limited a knowledge as that of its precise centesimal 
composition. Nevertheless, it would be wrong to leave the study of 
the more recent researches without drawing attention to certain of the 
numerical results obtained, which are more deserving of confidence 
than other-. 
The most characteristic and the most important of the elements 
which enter into the composition of haemoglobin is its iron. Iron is 
the typical element in a molecular group which exists and possesses 
identical chemical and physical properties in all the varieties of 
haemoglobin with which we are acquainted. Besides furnishing us 
with data by which the molecular weight of haemoglobin may be 
calculated, the amount of iron appears to hear a definite relation to 
the quantity of the dissociable oxygen and carbonic oxide which 
haemoglobin combines with. For these reasons, an extremely accurate 
determination of the iron in haemoglobin, carried out with all the 
precision which the present state of science permits of, has been a great 
desideratum. Such determinations have been carried out by Zinoffsky, 
Jaquet, and Hiifner (see p. 199). 
Hemoglobin of 
Fe per cent. 
Authority. 
Dog 
Horse 
Ox . 
Hen 
0-336 
0-335 
0-336 
0-336 
Jaquet. 
Zinoffsky. 
Hiifner. 
Jaquet. 
These observers have determined the proportion of iron in the 
oxyhemoglobin of the dog, the horse, the ox, the pig, and the hen. 
They have shown : First, that the amount of iron in the blood-colouring 
matter of these animals is decidedly smaller than had been assumed 
on the basis of the older analyses. Secondly, that in the animals 
mentioned the percentage of iron in the haemoglobin is identical, so 
that we may conclude that in these very different animals, in spite of 
