488 Prof. D. F. Harris and Dr. H. J. M. Creighton. [May 10, 



while the liquid filtered from the control was still methsemoglobin. We 

 concluded that we had here reduction effected by the active juice, while the 

 heat-inactivated juice was quite unable to effect any reduction. We had, in 

 fact, an illustration of the action thus described by the late Dr. G-amgee 

 in writing of methsemoglobin.* " The action of reducing agents reveals 

 .... that the molecule of loose oxygen of haemoglobin is still present in 

 blood which has been acted upon by nitrates for, in the absence of all traces 

 of oxygen, reducing agents first of all and instantaneously liberate oxyhemo- 

 globin, which is only afterwards reduced." In other words, the liver press 

 juice acted towards a solution of methtemoglobin exactly as the " reducing 

 agents" to which Dr. Garngee alluded in the paragraph just quoted. 



(b) The Action of Press Juice, on Hydrogen Peroxide. — It was found that 

 hydrogen peroxide Avas rapidly decomposed by small quantities of press 

 juice, a few drops of the juice causing relatively large quantities of 3-per- 

 cent, hydrogen peroxide to froth violently at room temperature. 



A few preliminary experiments on the rate of decomposition of hydrogen 

 peroxide by press juice were carried out. In these experiments the solutions 

 of the peroxide and the press juice were separately brought to the required 

 temperature before mixing. The mixture was then placed in a thermostat at 

 this temperature, and kept agitated by a mechanical device. From time to 

 time definite amounts of the mixture were removed with a pipette, acidified 

 with sulphuric acid, and the concentration of the hydrogen peroxide estimated 

 by titrating with standard potassium permanganate solution. As potassium 

 permanganate is slowly reduced by organic matter, the titrations were made 

 very rapidly, so as to lessen any error due to the presence of the proteins 

 contained in the juice. The amount of organic matter contained in the 

 mixture pipetted off for titration was always small, and, as very small 

 quantities of press juice were used, was practically negligible. 



A mixture containing 190 c.c. of O0950 molar' hydrogen peroxide and 

 5 c.c. of press juice (one week old) was prepared and kept at 25° C. It was 

 found that at the end of five minutes, 97'2 per cent, of the hydrogen 

 peroxide had decomposed, and at the end of 15 minutes 97*7 per cent. 

 Another experiment was carried out at 25° C. with a mixture containing 

 190 c.c. of 0'0950 molar hydrogen peroxide solution, 4 c.c. of distilled water, 

 and 1 c.c. of a press juice solution made by diluting one volume juice with 

 nine volumes of water {i.e. the concentration of the press juice in the 

 mixture was 1/50 that in the previous experiment). The following table 

 shows the change in hydrogen peroxide concentration with time : — 



* Gamgee, ' Schiifer's Text-book of Physiology,' 1908, vol. 1, p. 245. 



