132 THE ROYAL SOCIETY OF CANADA 



Dr. Creighton further showed that the iron ion originally trivalent 

 in the soluble Prussian blue is divalent in the colloidal complex of al- 

 bumen and the pigment. There has therefore been reduction. Further, 

 this colorless colloidal complex can be boiled for a short time without 

 its coagulating. For convenience, I call these phenomena, "The 

 Creighton effects". Now there is one significant difference as regards 

 the interaction between pure proteins and soluble Prussian blue and the 

 interaction betAveen press-juice and that pigment, namely, that whereas 

 there is no fading of the blue in the presence of protein at the end of 

 many hours, the blue in contact with fresh juice fades at once. These 

 are clearly not the same phenomena; for, for one thing, in the case of 

 the protein mixture the concentration of protein is very much greater 

 than it is in press-juice, but its effect is very much slower. 



Further, if the fading of the pigments is due to protein, then the 

 juice kept for three months in which the protein is well preserved and 

 is sterile, should reduce as well, or almost as well, as fresh juice; but 

 this is noticeably not so. 



Again, the rapid falling off in potency as regards reduction within 

 the first day would have no meaning as a phenomenon due to mole- 

 cular groupings and labile Hydrogen, whereas it has a meaning 

 with reference to the deterioration of the bio-chemical activit}^ of a 

 ferment. 



The fact that glycerol extracts of dried liver and of dried kidney 

 possess some reducing power, is more in accord with the conception of 

 that reduction being due to an enzyme than to a protein, for the gly- 

 cerol extract of dried liver had some recognisable reducing power, and 

 it could have taken up very little protein in "solution". Glycerol by 

 itself has no reducing power. 



Again, glycerol extracts deteriorate in potency with time for w^hich 

 there is no particular reason if protein be the active substance. Blood 

 at 40°C does not reduce ferric chloride, but liver-juice at this temper- 

 rature reduces it to ferrous chloride. There are proteins in both. While 

 giving due weight to Heffter's contentions and indeed recognising 

 certain phenomena of the fading of pigments in contact with proteins 

 which I have called "The Creighton effects," I still believe that vital 

 reduction is something distinct from these and is probably enzymic. 



VII. Indications that a tissue Endo-Enzyme exists. 



1. — The first consideration regarding reduction being due to an 

 enzyme is that whereas c|uite fresh juice vigorously and older juice more 

 gradually reduces several different kinds of chemical substances, boiled 

 controls do not do so at all. 



