Skctiox IV., 1913. [125] Traxs. R.S.C. 



On the Existence of a Reducing Endo-Enzyme in Animal Tissues 



By D. Fraser Harris, M.D., CM., D.Sc. F.R.S.E., 



Professor of Physiology and Histology in the 



Dalhousie University, Halifax, No va. Scotia 



Presented by Da. J. G. Adami, F. R.S.C. 



(Read May 29, 1913) 



/. Historical. 



It has for many years been recognised that both living and " sur- 

 viving" animal tissues possess deoxidising or reducing powers. 



Hoppe-Seyler ^ in 1883 was the first to draw attention to the pres- 

 ence of powerful reducing processess in living tissues. He suggested 

 that, through reduction, molecular oxygen was rendered active by 

 conversion into nascent oxygen and thus enabled to oxidise certain 

 constituents of tissues after the manner in which hydrogen-saturated 

 palladium-foil can oxidise indigo. 



Paul Ehiiich ^ two years later published his researches on the 

 reducing powers of tissues during life and at the moment of death. 



He classified tissues as regards their oxygen-avidity as follow — 



1. Those in which indo-phenol blue remains unchanged; these he 

 regarded as saturated with oxygen. Examples: heart, renal cortex 

 and the grey matter of the central nervous system. 



2. Those which reduce indo-phenol blue to indo-phenol white, 

 but not alizarine blue to alizarine white; Examples: striated and non- 

 striated muscle, gland-parenchyma. 



3. Those which reduce alizarine blue to alizarine white, that is 

 those with the greatest oxygen-avidity. Examples; lung, liver, fat- 

 cells and the gastric mucosa. 



Ehrlich injected the pigments subcutaneously intra vitam; he 

 noticed that a certain degree of heat arrested the reducing-power, but 

 he did not suggest that tissue-reduction was due to an enzyme. 



Between 1888 and 1909 J. dc Rey-Pailhade ^ wrote on a substance 

 he called ' 'philothion" which he regarded as one of the mercaptans and 

 indistinguishable from cysteine. To this substance he attributed 

 great importance in the fixation of oxygen by tissues. 



Spitzer* in 1894 noticed that after the death of the animal, while 

 the reducing powers of the tissues increased, the oxidising capacity 



