32 



dizing ferments, those that take up free oxygen and carry it to 

 another substance. In this class he places the ferments that pro- 

 duce a blue color with tincture of guaiac, such as that found in 

 potatoes and many other plants, b. Reducing ferments ; those 

 that have the power of changing the combined oxygen, produc- 

 ing not only an oxidation product but also a reduction product, 

 as alcohol and carbonic acid from sugar, by the action of yeast. 



In 1882 Clermont and Cheutard 25 obtained a considerable 

 quantity of pur-purgallin by exposing a solution of pyrogallol 

 containing 10% of acacia for several weeks to the action of air 

 but failed to recognize the true cause of the change in color. 



In 1883 H. Yoshida 26 was the first to discover that it was an 

 enzyme that acted as an oxidizing agent. He proved that the 

 milky juice of Rhus vernicifera was converted into a hard insolu- 

 ble black varnish by the action of a peculiar diastatic substance 

 contained in the juice and that the change took place in the pres- 

 ence of moisture, but more rapidly in moist oxygen. Also that 

 the change did not take place at all in the presence of dry car- 

 bonic acid gas, or in a solution that had been previously boiled, 

 thus proving that the color change was due to a distase which 

 was destroyed by heat. He also proved that the substance acted 

 upon by the enzyme had taken up oxygen, but did not give off 

 carbonic acid. 



Bouffard 27 states that the disease of wines which causes a 

 skin to grow on the surface of the wine is due to an enzyme and 

 that if the action is allowed to continue the wine becomes color- 

 less or light yellow. Later 28 he states that this action can be pre- 

 vented by heating the wine to 60 or by adding a very small 

 quantity of sulphuric acid. 



Gouirand 29 found that by filtering diseased wine through 

 porous tile and precipitating the filtrate with alcohol he obtained 

 a substance which, when added to sound wine, changed it rapidly 

 to the diseased condition. 



Martinand 30 obtained a substance in ripe grapes, pears and 



25 Compt. rend. 97, 1882, p. 1254. 

 20 Jour. Chem. Soc. 43, 1883, p. 472. 



27 Compt. rend. 118, 1894, p. 827. 



28 Compt. rend. 124, 1897, p. 706. 



29 Compt. rend. 120, 1895, p. 887. 



33 Compt. rend. 121, 1895, p. 502. Also 124, 1897, p. 512. 



