136 
found Yeast catalase to lose its activity at 70° C., although the dry 
yeast catalase could be heated to 100° C. without being destroyed. 
The kinetics of the decomposition of hydrogen peroxide by catalase 
(heniase) and various inorganic catalysts, especially the colloidal metals 
(inorganic ferments), has been exhaustively studied by Senter ( 400 ) and 
also by B redig ( 96 > 97 ). The decomposition of hydrogen peroxide both 
by catalase (hemase) and by the colloidal metals has been shown 
to conform to the law of an irreversible monomolecular process. 
With constant quantities of the catalyst the velocity of the decompo- 
sition has been found to be directly porportional to the concentration 
of the peroxide within certain limits. At small concentrations, 
however, both with the ferment and inorganic catalysts, the decom- 
position is proportionately slightly greater than with greater concen- 
trations. In other words, the hydrogen peroxide itself, or some 
impurity which it contains, slightly inhibits the decomposition. With 
constant amounts of the hydrogen peroxide, especially at small con- 
centrations, the decomposition has been found to be proportional to 
the quantities of catalase Chemase) or inorganic catalyst present. 
With more concentrated solutions of the catalase, however, both 
with the hemase and colloidal metal, the velocity of the reaction 
increases more rapidly than the increase in the concentration cf the 
catalyst. A rise of temperature of 10° C. increases the velocity of the 
decomposition of hydrogen peroxide by platinum 1.7, and by hemase 
1.5, whereas, according to van 't Hoff ( 216 ) for most chemical processes 
the velocity is doubled by such an increase in temperature. 
The power to decompose hydrogen peroxide as shown both by 
hemase and the inorganic catalvsts is greatlv inhibited bv certain 
poisons and foreign substances, such as hydrocyanic acid, hydrogen 
sulfide, hydroxyl a, min , metallic nitrates, etc., at very great dilutions; 
and in this connection Loevenhart and Kastle ( 275 ) made the inter- 
esting observation that the activity of the catalase of hog liver was 
greatlv inhibited bv ammonium sulfocvanide. whereas it was ren- 
dered even more active by thiourea. 
Since the recognition of catalase as a specific enzyme its occur- 
rence and distribution in various animal and vegetable tissues has 
been investigated bv a number of observers. We have seen that 
Spitzer ( 407 ) measured the catalytic power of various animal tissues 
toward hydrogen peroxide with the view of determining their relative 
oxidizing power. The various animal tissues have been found to vary 
greatly in catalytic power. Thus, according to Battelli and Stern ( 35 ) 
the liver contains the most and the brain the least amount of 
catalase of anv of the tissues examined. Thev foimd, further, that the 
tissues of the guinea pig contain more catalase than those of the frog. 
Similarly Jolles and Oppenheim ( 229 ) found that the tissues of warm- 
