SPECIFIC OXYGEN CAPACITY 57 



When it is remembered that the whole of these operations, both 

 iron analyses and gas analyses, could be carried through successfully 

 in a day, it will be clear what an advance Peters made by the use of 

 the then modem technique, both as regards the concordance of his 

 figures, and the certainty with which he has been able to put them 

 forward. His figures for the volume of oxygen per gram of iron are 

 as follows : 



Average ... 391 



It is not very easy to discern the processes by which conviction 

 grows in the mind ; probably the mere inspection of the figures given 

 is sufficient to convince the reader that so far as the relation of the 

 respiratory oxygen to the iron of haemoglobin is concerned, these 

 quantities are related in the proportions of two atoms of oxygen to 

 one of iron. To me, who had the privilege of seeing Peters' work 

 from week to week, conviction came in a slightly different way; it 

 developed as it were like the image on a photographic plate. As one 

 experimental difficulty after another was overcome, as one source 

 of error after another was weeded out, as the worker himself developed 

 in skill and in capacity, just so surely did the results which he obtained 

 approach the theoretical figure with greater certainty until, at the 

 end, when all the difficulties had been overcome, and when Peters 

 himself had attained to the rank of a first-rate exponent of the 

 technique, I arrived at a stage of conviction in which I never doubted, 

 when he undertook an experiment, that the result would be between 

 385 and 405. Perhaps there could be no surer proof that all thought 

 of the wide differences between different kinds of haemoglobin, 

 alleged to exist by Bohr and others, had passed out of our horizon 

 than the fact of our almost laughable concern at the end as to why 

 the average figure was 391 and not 401. We in the laboratory thought, 

 perhaps, that Peters did not perform sufficient experiments to obtain 

 a true average, or that some trace of methsemoglobin was always 

 present, or that some trifling error was always present in the 

 standardisation of the apparatus used. 



A very careful recalibration of the apparatus by another method 

 was undertaken by Burn(i5), who obtained a result 2-5 per cent, 

 higher than that given by the method which Peters used. 



