ROLE OF REDUCTASE IN TISSUE RESPIRATION 55 



Reductase certainly acts like a reducer in an alkaline medium. 

 Acid, therefore, added to the soluble Prussian blue and gelatine 

 mixture prevents that complete reduction in the capillaries ot 

 an injected organ which occurs in its absence. Histologists 

 recommend acetic acid being added to this particular injection 

 mixture in order to prevent " fading by the alkaline tissues." 

 That the inorganic salts ot the blood do not reduce soluble 

 Prussian blue is shown by the lact that when the blue and the 

 red (of the blood) meet in the large vessels they form purple in 

 those cases where the blood is not washed out previous to 

 injection ; but if the blue were reduced to the colourless state, 

 the blood would be red in the large vessels, whereas it is always 

 purple when the one pigment does not predominate over the 

 other. It is hardly necessary to say that reduction was not due 

 to products of putrefaction, for not only were the juices kept 

 under toluene, but the reducing power falls off with age while 

 the products of putrefaction must necessarily accumulate as 

 time goes on. The next factor which had to be eliminated was 

 the supposed reducing power of proteins (colloids) ; this was 

 taken up by one of us. 1 Briefly stated his conclusions were : 

 colloids such as gelatine and egg-white reduce soluble Prussian 

 blue with great rapidity at 100 °C, in about half an hour at 

 60 ° C, while the reduction is barely perceptible at room tempera- 

 ture at the end of many hours. It was shown that the protein 

 formed a colourless compound with the pigment, and that 

 reduction was due to the removal of a positive ionic charge. 

 Seeing, then, that fresh liver or kidney juice at room tempera- 

 ture can reduce soluble Prussian blue to the leuco condition 

 within sixty seconds, the agent operative in the case of colloidal 

 reduction is not that which we have been investigating in 

 tissue juices. 



We think it is possible that these colloidal phenomena 

 worked out by Creighton are the reductions which Heffter has 

 studied. Heffter 2 holds that the so-called reductase reductions 

 are not vital (enzymic), but are all due to the interaction of 

 colloids and pigments. He says that crystallised egg-albumen 

 can effect reduction. The blood-proteins certainly cannot do so 

 either at room temperature or at 40 °C. 



Now, however interesting and important the study of the 



1 Creighton, H. J. M., Nova Scotian Inst. Sa'., 13 (2), p. 61 (1911-12). 



2 Heffter, Archiv f. Path. undPharm. Festschr.f. 0. Schmiedebcrg, p. 253 (1908). 



