424 SCIENCE PROGRESS 



precipitated from the juice by alcohol. This property, how- 

 ever, returned on the addition of hydrogen peroxide ; showing 

 that the substance precipitated and rendered inactive could be 

 replaced by hydrogen peroxide. Bach showed also that if 

 the taking-up of oxygen by an auto-oxidisable substance — i.e. 

 the formation of a peroxide — was prevented (by passing hydro- 

 gen in coal gas through the system), no oxidation of guiacum 

 by peroxidase would take place. The oxidation of the guiacum 

 took place, however, if air was admitted or hydrogen peroxide 

 added. • 



The earlier observations of Yoskida had shown that the 

 production of lacquer varnish from the sap of the lac tree was 

 dependent on an enzyme which brought about oxidation, and 

 which he called laccase. This was the first vegetable oxidising 

 enzyme to be discovered. It had been noticed previously 

 that salts of manganese, iron or copper acted somewhat like 

 peroxidase on the decomposition of hydrogen peroxide. Follow- 

 ing up this point, Bertram showed that the properties of laccase 

 depended to a great extent on the presence of manganese in its 

 constitution. Later Dony-Henault was able to prepare an 

 artificial laccase. 



More recently artificial oxidases having more general pro- 

 perties have been prepared. Dimichelis (191 7) found that 

 certain metallic colloidal compounds exerted catalytic action, 

 and he prepared an artificial oxidase having the chemical con- 

 stitution Cua.Fe. (Cue). The term oxidase in this connection 

 is loosely used, as more generally it is reserved for the system 

 containing a peroxide and peroxidase. 



An artificial oxidase system was elaborated by Reed (19 16) 

 as a result of his work on the charging of colloidal platinum 

 with oxygen. This investigator showed that the peroxidase 

 extracted from potato could be charged with oxygen by 

 potassium permanganate. It could then oxidise iodic acid 

 till the charge was exhausted. He concluded therefore that 

 an oxidase was a substance of high oxidation potential formed 

 by charging a peroxidase previously with oxygen or by associ- 

 ating it with a peroxide. 



Every year brings further evidence as to the part played by 

 peroxidase in the life of organic matter. Graham (1916) 

 demonstrated by means of naphthol and H2O2 that there exists 

 in the granules of leucocytes and myelocytes a peroxidase of 

 the peroxide type. The importance of this in the destruction 

 of toxic agents in the blood is obvious. 



In the plant world, loss of toxicity due to enzyme oxidation 

 was instanced by McNair (191 7). He found that the exuding 

 sap of Rhus diversibola rapidly became oxidised by the air 

 and lost its toxic properties, while subsequently he extracted 



