200 HEMOGLOBIN. 



Were we to- admit the accuracy of the work of all the observers, 

 whose results are exhibited on the table on p. 199, we should be forced 

 to the conclusion that haemoglobin is a body which does not only vary 

 considerably in composition in different animals, but does not possess a 

 constant composition even in different individuals of the same species. 

 Thus, whilst Kossel found the percentage of carbon in the oxyhaemoglobin 

 of the horse to be 54'87, and the mean of a large number of analyses 

 by Kossel, Otto, and Biicheler gave 54*68, Zinoffsky, as a result of his 

 analyses (only two in number, so far as the carbon and hydrogen are 

 concerned !), found the percentage of carbon in the haemoglobin of the 

 horse to be 51/15 (!!). A body in which the carbon differs by 8*72 per 

 cent, in different specimens cannot, it wijl be argued, be a chemical indivi- 

 dual. But to draw this conclusion in reference to haemoglobin from the 

 facts in our possession would certainly be an error. The discrepancies 

 between the results of the analyses of the haemoglobin of the same 

 animals are doubtless due to differences in the purity of the substance 

 analysed, and to errors of analysis. The preparation of perfectly pure 

 oxyhaemoglobin, entirely free from contamination with other con- 

 stituents of the blood corpuscles and from products of decomposition, is 

 much more difficult than has, until very recently, been supposed. In 

 the attempt to purify the substance by crystallising it as frequently as 

 practicable, nearly all observers have in all probability decomposed it, 

 and have afterwards analysed a mixture of oxyhaemoglobin and products 

 of its decomposition. How far this is the source of the above discrep- 

 ancies must now, in the light of recent spectrophotometric work, be 

 carefully enquired into. Moreover, assuming that perfectly pure crystal- 

 lised oxyhaemoglobin is at the disposal of the analyst, the task of drying 

 without decomposing it is one of peculiar difficulty, concerning the 

 method of execution of which the chemists who have carried out the 

 researches under discussion have been by no means agreed. Thus, whilst 

 some (following Hoppe-Seyler's directions) have dried the oxyhaemoglobin 

 intended for analysis, in the first instance in vacuo at C., and only 

 afterwards at higher temperatures, others (Zinoffsky, Hiifner, Jaquet) 

 have dried the substance in vacuo at ordinary temperatures (15 to 

 18 C.), and subsequently at 110 to 115 C. 



It is conceivable, nay probable, that some of the differences in the results 

 of different observers may have depended upon the above-mentioned differ- 

 ence in the treatment of the substance analysed. But, unquestionably, some 

 of the best marked differences must depend upon differences in the 

 method of analysis employed (e.g. where one observer determines the N in 

 oxyhsemoglobin by Will and Varrentrapp's method, whilst another employs 

 Dumas' method), and upon accidental errors of analysis, which can easily be 

 rendered obvious, by making a considerable number of analyses. 



For instance, it appears to me that the percentage of carbon given by 

 Zinoffsky, 1 as representing the proportion of this element in the hsemoglobin 

 of the horse, must be due to imperfect combustion. Whilst this observer 

 carried out the determinations of iron and sulphur in the haemoglobin of the 

 horse in the most elaborate and perfect manner, making many analyses of 

 each of three separately prepared specimens of crystallised haemoglobin, he 

 rested satisfied with only two determinations of carbon and hydrogen, and 

 two determinations of nitrogen (the latter by the method of Will and 



1 "Ueber die Grosse des Hamoglobinmoleciils," Ztschr. f. physiol, CJiem., Strassburg 

 1886, Bd. x. 



