147 



pounds, the temperature being 112 degrees C. It required thirty minutes 

 to reach this pressure. The solutions were talven out as quiclilj^ as pos- 

 sible and cooled in the snow at once, after which pyroeatechin was added 

 to each. The white flour extract had a white precipitate formed by the 

 heat action, but this was an unpurified extract. The six days germination 

 extract remained clear. A slight reddening appeared in the white flour, 

 and a slight darkening in the other. (They were compared with extracts 

 without the pyroeatechin.) This became more marked, the longer the 

 extract stood. At the end of seven days the discoloration was quite 

 marked. 



The action of the oxydases is a very interesting and practical sub- 

 ject, as their action explains many puzzling phenomena, which were 

 formerly classed as oxidations, but the cause and conditions of which 

 were unknown. The composition of the oxydases is unknown, and con- 

 sequently it is impossible to determine the number of oxydases — if there 

 be numbers of them— except by the differences in reactions and condi- 

 tions. From considering oxidation as a purely physiological process, as 

 exemplified by respiration, and which only took place through vital proc- 

 esses, one has to consider oxidation from the opiwsite extreme.* 



The most common manifestations of the action of oxydases are the 

 discolorations of beets, carrots, apples, and many plant tissues and juices, 

 besides the browning of wines and other liquids. The juice of the plant 

 Rhus vernicifera from which lac varnish is made contains an oxydase 

 which is, perhaps, the most widely known. Many of these have been in- 

 vestigated, and have been found to have certain points in common, though 

 differing in others. They are all susceptible to the reaction of the me- 

 dium, and also the temperatures at which they are rendered inactive vary 

 within certain limits. The browning of wines is prevented by a tempera- 

 ture between 70 and 80 degrees C. or by Pasteurization at 60 to 62 de- 

 grees.f A large number of oxydizing enzymes which are found in differ- 

 ent plants and animals are mentioned by Oppenheimer|, the most resistive 

 of which succumb to boiling temperature. 



The enzyme which exists in the wheat grain, both in the quiescent 

 and germinated grains, from the differences in degree of discoloration of 

 extracts, and also action on phenols, exists in least amount in the white 



♦Pozzi-Escot, M. E. Les Diastases at Leures Applications, 1900. 



tLafar. F. Technical Mycology, p. 401, 1898. 



t Oppenheimer, C. Ferments and their Actions, 1901. 



