326 OSCAR RIDDLE. 



TABLE II. 



SHOWING SOME OF THE KNOWN FACTS OF CHEMICAL EXPERIENCE CONCERNING 



THE SUCCESSION OF OXIDATIONS OF TYROSIN AND CLOSELY RELATED 



BODIES TO MELANIN PIGMENTS. 



Tyrosin = HO- -CH 2 CH(NH 2 )_ COOH 1 Colorless. 



P-oxyphenyl-pyrotartaric acid= HO c^ J> CH 2 CO COOH 1 " 



CH 2 CO COOH 1 

 >H 



Hydrochinon-pyrotartaric acid = / \ CH 2 CO COOH 1 " 



Homogentisic acid 4 = ... ( \ CH 2 COOH 1 " 



HO 



,OH 



Gentisic acid = N COOH " 



HO 



Melanogen ( ) " 



Melanin ( ) (White)? 2 



Melanin ( ) Pale yellow. 3 



Melanin ( ) Deep yellow. 3 



Melanin ( ) Red. 3 



Melanin ( ) Brown. 3 



Melanin (C 50 H 58 N g SO J2 ) Black. 3 



Melanin (C 45 H 78 N 10 SO 20 ) (White)? 2 



and conditions ; these may vary or change from year to year 

 a power of oxidation not possessed by the individual during 

 many early years of life being attained at manhood, or vice versa. 

 Bateson ('02) has seen fit to claim that (p. 133, note) alkapto- 

 nuria is the result in inheritance of the union of " two recessives." 

 Garrod has concurred in the view. But in the light of the in- 

 constant and intermittent character of the phenomenon, it seems 

 necessary to draw a directly opposite conclusion. 



1 This according to Neubauer ('08). 



2 See discussion of Spiegler's work ('03), etc., p. 328 of this paper. 

 3 These from Gessard ('03) and from Bertrand ('08). 



4 Concerning the formation of homogentisic acid from tyrosin in plant tissues, see 

 Schulze and Castoro, Zeit. f. Physiol. Chem., Bd. 48, p. 396, 1906. 



