266 EXISTENCE OF A REDUCING ENDO-ENZYME 



Ringer's solution added warm to Prussian blue produces 

 no change of colour beyond that due to a corresponding 

 dilution with water. 



None of the salts of the tissues, NaCl, KC1, Na 2 CO 3 , 

 Ca32(PO 4 ), Na 3 PO 4 in strengths under 1% solution added 

 warm singly or in any kind of combination, caused any fading 

 to the green or to the leuco condition, whereas the subsequent 

 addition of such a reducer as pyrogallol at once caused fading 

 through green to white. 



When the gelatine and Prussian blue mixture is used to 

 inject organs still living, the pigment is reduced, as I believe, 

 by the agency of the living tissues; and histologists aware of 

 this fading, attribute it to"contact with the alkaline salts of 

 the tissues." 



Thus Rawitz( 16 ) recommends that a little acetic acid be 

 added to the injection-mass to prevent the "fading" by 

 alkaline tissues. 



Naturally, this criticism applies only to pigmentary 

 substances, and has no applicability to non-pigmentary salts 

 used to demonstrate bio-chemical reduction. 



(b) The next source of fallacy one must bear in mind is 

 the possible putrefaction of the proteins of press-juice in 

 in specimens of juice kept for more than a few daj^s. 



Toluene was the antiseptic used for all press-juices; some 

 kind of antiseptic is absolutely necessary, although Battelli( 23 ) 

 has emphasized the inhibitory effect of antiseptics on the 

 enzymic and respiratory powers of tissues. The antiseptic 

 used had obviously to be one which would not of itself bleach 

 or reduce the pigments or other substances and would not 

 act as an activator or inhibitant of the enzyme. Sodium 

 fluoride and many other substances had to be rejected on 

 some of those grounds. Toluene apparently prevented 

 putrefaction in the press-juices used. Had the reductions in 

 old juice (two to six weeks old) been due to putrefaction or 

 autolytic substances, then the reducing power should have 



