76 Frederic Czapek . — The Anti- ferment Reaction in 
alteration in the amount of the enzyme present, or by some retardation of 
the oxydasic effects. The substance reducing nitrate of silver, which 
increases in amount in stimulated roots, was recognized to be a phenol acid, 
but could not be more closely identified. Analogous changes were also 
found in the tip of the cotyledon of Arena after geotropic stimulation. 
These results, though of obvious significance, may for the moment be 
passed over. 
To place my results on an unassailable basis a quantitative method 
was necessary, and in my search for such a method I was for some time 
unsuccessful. In the year 1900 it was observed in my laboratory that 
roots of Lupinus albus , being in an asphyxiated state or in chloroform 
narcosis, showed numerous spherical crystals which could be recognized as 
those of tyrosin ( 2 ). I immediately saw that this precipitate of tyrosin 
did not occtir in the root-tip or in the youngest parts of the growing 
region, just in the parts where I had observed the strongest reduction of 
silver. It seemed possible that the reducing substance and the tyrosin 
crystals were genetically connected. To test this Lupine roots were treated 
with chloroform water until they were rich in tyrosin crystals, when they 
were further digested at 28 0 Cels, in a chloroform atmosphere. At 
first the cells containing tyrosin did not show any silver reduction ; but 
after a few days the crystals of tyrosin disappeared and the cell-content 
reduced ammoniacal solution of silver very strongly. Roots of Lupimts 
were then finely ground and treated with chloroform water at 28 0 until the 
Millon reaction could not be observed. I then added a little pure tyrosin 
from Merck, Darmstadt. This also disappeared, as could be seen by the 
Millon test becoming gradually weaker and finally imperceptible. But the 
mixture was getting an exceedingly strong power of reducing silver ; so 
that the suggestion that a silver-reducing substance is produced from 
tyrosin was certainly confirmed. It was also shown that this decompo- 
sition of tyrosin is connected with enzyme action. 
Now since the year 1891 a substance has been known arising from 
tyrosin in human and animal metabolism, and possessing an active power of 
reducing silver. This substance was prepared by Wolkow and Baumann (3), 
and must be regarded according to these authors as the next higher 
homologous acid to gentisinic acid. This substance C 8 H 8 0 4 received in 
the nomenclature of Tiemann the name of * homogentisinic acid 5 : 
Gentisinic acid : 
C 7 H 6 0 4 
COOH 
/\>„ 
Homogentisinic acid : 
Cg H 8 O 4 
CHj. COOH 
