SPECIFIC OXYGEN CAPACITY 



59 



himself, the average figure came to 391; (6) that on a recalibration 

 by Burn it came to 401 ; (c) that better methods of calibration now 

 exist; but the particular apparatus used by Peters has long since 

 vanished, even the type is no longer made. 



There remains the possibility therefore that some 2 per cent, of 

 the iron present was contained in substances which do not yield their 

 oxygen to ferricyanide. 



Fig. 13 a. Apparatus used by Peters. 



KJJ 



Fig. 13 h. A more recent model. 



If one enquires what these substances may be, first there is met- 

 hsemoglobin. Two parts of methaemoglobin are not very easy to 

 detect in one hundred parts of oxy haemoglobin. The spectrum would 

 not show them and it would require very accurate analytical methods 

 to do so. 



The second substance, known as "inactive haemoglobin," is to be 

 considered. Could 2 per cent, of the haemoglobin have been in 

 the inactive state ? Peters unconsciously reduced his problem to its 



