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SOURCES OF PEROXIDASE AND METHODS FOR ITS PREPARATION, 
Among plants the peroxidases are almost universally distributed. 
There are but few, if any, plant tissues which do not give peroxidase 
• reactions at some stage of their growth and development. So, 
likewise, they are widely distributed in animal tissues and secretions ; 
saliva, milk, pus, etc., show typical peroxidase reactions. By means 
of certain of the very sensitive peroxidase reagents employed by 
Kastle and Porch ( 246 ) in their study of the peroxidase reaction of milk, 
Doctor Roberts, working in this laboratory, has been able to stain a 
large number of the leucocytes in fresh blood smears, indicating that 
in the blood the peroxidase proper is confined to the white cells. 
Thus with a reagent containing cresol, para-plienylene diamin and 
hydrogen peroxide, the leucocytes are stained blue. 
By precipitation with alcohol, Linossier ( 273 ) prepared a peroxidase, 
free from oxidase, from pus. In many instances plant peroxidases 
may be obtained free from oxidases by heating the aqueous extract 
to 70° C., at which temperature the oxidase is destroyed. Aso ( 16 ) 
has separated plant peroxidases from oxidases by fractional precipi- 
tation with alcohol, in which solvent the oxidases are soluble to a 
considerable extent. 
As sources of peroxidase, Bach and Chodat ( 27 ) have employed the 
pumpkin ( Kurbisfruchten ) and the root of the horse-radish ( Meer - 
rettigwurzel ) . In order to obtain the peroxidase, these authors 
proceed as follows: Two kilograms of finely grated horse-radish 
root are allowed to stand several hours at ordinary temperature in 
order to completely hydrolyze all glucosides that may be present. 
The mass is then digested for four to five days with 80 per cent 
alcohol in order to dissolve the essential oils. The reddish alcoholic 
extract is then poured off, the residue is washed with 80 per cent 
alcohol, pressed, and extracted with about 8 liters of 40 per cent 
alcohol. The 40 per cent alcoholic extract, which shows strong- 
peroxidase reactions, is then reduced to small volume at 30° C. in 
vacuo, filtered, and absolute alcohol added until a turbidity is pro- 
duced. The white precipitate thus produced is dissolved in a small 
amount of water, again precipitated with absolute alcohol, and dried 
in vacuo. In this way a yellowish white gummy mass is obtained 
which is very soluble in water and readily soluble in 40 per cent 
alcohol. As ordinarily obtained these peroxidase preparations 
strongly reduce Fehling’s solution. By re-solution in water and 
re-precipitation with alcohol, peroxidase preparations may be obtained 
which no longer reduce Fehling’s solution. The purest peroxidase 
preparations obtained by this method give ammonia and substances 
having the odor of pyridin on heating with caustic soda, but failed to 
show the ordinary reactions for proteid. On heating to boiling, „ 
solutions of the peroxidase were found to lose their activity; on 
