268 EXISTENCE OF A REDUCING ENDO-ENZYME 



tions. Heffter's contention is that proteins apart from life 

 can actively reduce. 



Confining ourselves first of all to Prussian blue, it is 

 certain that all proteins do not cause this pigment to fade, at 

 least within times measured by hours and at room-temperature. 

 For one thing, gelatine itself without acid does not cause 

 soluble Prussian blue to fade even before it is injected into an 

 organ and even when heated. 



It is well known that this injection-mass mixed with the 

 blood-proteins in the large vessels of mammals at body temp- 

 erature is not reduced or caused to fade. Neither is methylene 

 blue; those pigments remaining blue produce along with the 

 red of the blood a purple colour. If Heffter be correct, we 

 should expect the blood-proteins to reduce these pigments to a 

 pale green or leuco condition, this they certainly do not do. N 



If one mixes a saline solution of pure serum-albumen or 

 serum-globulin with Prussian blue, no fading takes place at 

 room temperature within 24 hours. 



In 1912 my co-worker at that time, Dr. H. J. M.Creigh- 

 ton( 18 )of the Dalhousie University, Halifax, N. S., investigated 

 this subject with very great care and published his results in 

 the Transactions of the Nova Scotian Institute of Science. 



Dr. Creighton showed that if one mixes 10 c.c. of a 15% 

 solution of egg-white in dilute NaCl with 10 c.c. of a 0.05% 

 solution of soluble Prussian blue (potassium ferric ferrocyan. 

 ide) and keeps the mixture at 60 C the colour will have, faded 

 at the end of an hour. The fading is gradual. Dr. Creighton 

 writes, "With pure white-of-egg at a higher temperature, the 

 decoloration of the soluble Prussian blue was found to proceed 

 with greater rapidity". On the other hand, white-of-egg 

 solution and 0.05% Prussian blue mixed and kept at room 

 temperature, showed no fading or change of colour at the end 

 of six hours. 



Dr. Creighton further showed that the iron ion originally 

 trivalent in the soluble Prussian blue is divalent in the 



