260 EXISTENCE OF A REDUCING ENDO-ENZYME 



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. de 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 

 oxidizing capacity rapidly disappeared. He also noticed that 

 the temperature of 100° C might not always destroy the 

 reducing power, whereas it always destroyed the oxidizing. 



In 1895 Sir Victor Horsley and A. Butler Harris(^)made 

 a report to the Scientific Grants Committee of the British 

 Medical Association on the appearance of tissues of animals 

 injected subcutaneously inti^a vitam with methylene blue. 

 In the milk and in the urine a/leuco form was found. On 

 faradization of the living cortex cerebri these workers demon- 

 strated a state of reduction around the stimulated spot at a 

 time when the blue coloration elsewhere was at its height. The 



