126 THE ROYAL SOCIETY OF CANADA 



rapidly disappeared. He also noticed that the temperature of 100°C 

 might not always destroy the reducing power, whereas it always des- 

 troyed the oxidising. 



In 1895 Sir A'ictor 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 intra 

 vitam with methyene blue. In the milk and in the urine a leuco form 

 was found. On faradisation of the living cortex cerebri, these workers 

 demonstrated a state of reduction around the stimulated spot at a 

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

 coloration was not due to ionised hydrogen at the kathode, for when the 

 cortical excitability had disappeared, the reduction of the pigment 

 at a stimulated spot could no longer be obtained. 



These workers therefore recognised the simultaneous activity of 

 two processes, oxidation and reduction, the precise colour at any mo- 

 ment being the result of the relative predominance of the one process 

 over the other. Frequently they found that oxidation prevailed over 

 reduction. 



In 1896 I* found that living tissues of cat and rabbit — kidney, 

 liver, heart, glands — reduced the blue potassium ferric ferrocyanide in 

 the Prussian blue and gelatine injection mixture to the green or 

 white leuco state of the di-potassium ferrous ferrocyanide which on ex- 

 posure to air slowly, or by treatment with hydrogen peroxide rapidlj'', 

 became blue again. 



The pigment was reduced only in the washed out, smaller vessels 

 and capillaries; in presence of blood not washed out of the larger 

 vessels, the Prussian blue remained unreduced. The colour of the 

 blood was therefore a purple. 



In 1899 the term "reductase" as indicating a tissue-ferment 

 capable of effecting reduction-processes, was first used by Abelous 

 and Gerard.'' 



Pozzi-Escot^ in 1902 published the results of work on the reducing 

 action of vegetable and animal tissues on solutions of indigo, litmus 

 and Prussian blue out of contact with air. He confirmed Rey-Pailhade 

 in finding that the tissues could form hydrogen sulphide from sulphur, 

 and could reduce potassium iodide when out of contact with air. 



He held that a reductase might be suspected when a living tissue 

 decomposes Hj Og, but does not affect a mixture of guaiacum and HjOj. 



C. A. Herter" in 1904 and 1905 published two papers on the reducing 

 powers of living tissues. He injected methylene blue intra vitam. 

 He stated that ' 'the liver usually retains a high grade of reducing activity 

 for several hours after death ". He found lung, suprai-enal capsule and 



*At this date I had seen only Fhrlich's paper on oxy<;en avidity. 



