XIV ORIGIN OF PIGMENTS 291 



hsemoglobin of the blood, and that, therefore, its 

 amount is a direct measure of the rapidity of the 

 degenerative changes occurring in the haemoglobin. 

 From some recent work it would, however, appear 

 that there is not this direct relation between the 

 pigment and haemoglobin. Drs. John Abel and 

 Walter Davis, in the course of a laborious investiga- 

 tion on the pigments of the negro's skin and hair, 

 found that the pigment granules of the epidermal 

 cells contained a substratum of non- pigmentary 

 substance, apparently of the nature of a highly 

 resistant proteid. When this proteid is removed the 

 pigment is readily soluble in dilute alkalies, from 

 which it may be precipitated by acids. It contains 

 carbon, nitrogen, oxygen, hydrogen, and sulphur, but 

 in the pure state very little iron. It is the presence 

 of sulphur without any considerable amount of iron 

 which, in the opinion of the authors, makes an origin 

 from haemoglobin very doubtful. The proteid which 

 is also present in the pigment granules contains a 

 considerable amount of iron as well as of other in- 

 organic constituents. Floyd showed in 1876 {Chem. 

 News, vol. xxxiv. p. 179) that the skin of the negro 

 contains about twice as much iron as the white skin, 

 but this is apparently due to the proteid and not 

 to the actual pigment itself The investigators are 

 of opinion that the pigment originates from some 

 proteid of the blood or " parenchymatous juices." 

 Similarly Dr. Sheridan DeMpine considers that 

 melanin is elaborated out of the plasma of the blood 

 and is not a derivative of haemoglobin. On the 

 other hand, he is of opinion that hemoglobin itself 

 is perhaps manufactured from some " antecedent. 



