ALKAPTONUKIA 



507 



It was a difficult matter for Wolkow and Baumann to explain the 

 transformation of tyrosin to homogentisic acid. 



COOH 



H om o oentis'ic 



In the tyrosin molecule the OH group is one and in the para position, 

 whereas in the alkapton molecule the OH groups are two, one in the ortho 

 and one in the meta position. Since they knew of similar changes pro- 

 duced by bacteria in other instances, Wolkow and Baumann suggested that 



