22 HEMOGLOBIN 



Anson and Mirsky did, however, stress one difference between 

 "haematin" and "haem," namely, the difference in solubility, and 

 their observation was evident enough when demonstrated, particularly 

 in acid solution. When acid is added to blood a dark brown solution 

 is formed with the spectrum of haematin which is given in the text- 

 books. When Teichmann's crystals (haemin) are treated with NaOH 

 and the solution rendered acid a precipitate gradually forms ; it goes 

 on forming until the whole of the pigment is precipitated. The 

 natural inference would be that haematin in acid solution was very 

 soluble whilst haem in an acid medium was extremely insoluble. 



Just at this point Keilin(4) made the interesting observation 

 referred to in Chapter ii that the apparent difference between the 

 "haem" and the "haematin" in acid was a question of environment. 

 The reason why haematin produced by the addition of acid to blood 

 does not come down is because the particles when formed are sur- 

 rounded by a protective colloid which keeps them in suspension. 

 If " acid haem " be made as Anson and Mirsky made it but in a solution 

 of about 0*2 per cent, gum arable instead of an aqueous solution the 

 "haem" which is formed presents the general properties of "acid 

 haematin," it remains in solution and gives the same spectrum as 

 haematin. It must be concluded that "haem" and "haematin" are 

 the same substance. This discovery naturally raises the question of 

 whether there is any great difference between reduced haem and 

 haemochromogen, but here Keilin has entirely confirmed Anson and 

 Mirsky, and of course it was the fact of haemochromogen being a 

 conjugated protein which constituted the essential point of Anson 

 and Mirsky's work. 



If the substance C34H3oN404FeOH which bears the names "haem" 

 and "haematin " be made in gum arable so that the identity is evident 

 and then reduced the reduced product is just what Anson and IVIirsky 

 described as reduced haem so far as may be judged from its spectrum, 

 and bears just the relation to haemochromogen which Anson and 

 Mirsky discovered. Keilin therefore caUs in question the existence of 

 a conjugated protein corresponding to Anson and Mirsky's "alkaline 

 haematin," he believes that when alkali is added to blood the protein 

 is broken off the iron porphyrin portion, for which he retains the 

 word "haematin," and that therefore C34H3oN404Fe and protein are 

 formed. Keilin believes further that when the mixture is reduced 

 the protein and the iron porphyrin nucleus unite to form haemo- 

 chromogen. His scheme is as follows: 



