123 
iron. In this connection it is of interest to note that so far as is known 
the most stable and most perfect oxygen catalysts occurring in the 
animal organism contain either copper or iron. According to TTells 
(verbal communication) the blood of certain marine forms has been 
found to contain zinc. The fact that hemoglobin and its iron-con- 
taining derivatives are all capable of inducing the oxidation of such 
substances as guaiacum, plienolphthalin, etc., by means of hj'drogen 
peroxide or other compounds of this nature, whereas the iron-free 
blood pigments can not accomplish such oxidations, speaks strongly 
in favor of the assumption that the activity of such oxygen carriers 
is dependent on iron in organic combination. {See Kastle ( 2J|0 )), 
tl Chemical Tests for Blood,” Bulletin No. 51, Hygienic Laboratory.) 
In this connection it is also of interest to note that Floyd ( 171 ) found 
nearly twice as much ash in the skin of the negro as in that of whites, 
and nearly twice as much iron in the ash of the negro’s skin as in the 
ash of whites. According to this author the pigment appears to origi- 
nate in the outer layer of the true skin, and in all probability is the 
product of the alteration of the red coloring matter of the blood. It 
has also been shown experimentally that certain iron salts accelerate 
biological oxidations. Thus Battelli and Stern ( 36 ) have found that 
the quantity of carbon dioxide produced by the action of an extract 
of the muscle of the horse or dog on calcium lactate is considerably 
increased by the presence of small amounts of ferrous sulfate. 
It has been shown by Bertrand ( 56 ’ 57j 58 ) that the oxygen-carrying 
power of laccase is in some way associated with the presence of man- 
ganese. By fractional precipitation with alcohol he was able to 
resolve a certain specimen of laccase into two portions, one of which 
was poorer and the other richer in manganese than the original sam- 
ple. The oxidizing powers of these three specimens were proportional 
to their manganese content, as may be seen from the following table: 
j 
He also succeeded in showing that the laccase contained in lucerne 
is poor in manganese and comparatively inactive toward hydro- 
quinon. In the presence of a small amount of manganese (1 milligram 
in the form of the sulfate) the oxidizing power of lucerne laccase is 
greatly increased. That such is the case is evident from the quanti- 
ties of oxygen absorbed by a solution of hydroquinon in the presence 
No. of 
speci- 
men. 
Quantity 
of manga- 
nese in ash. 
Oxygen absorbed 
in li hours by 50 
c. c. of a 2 per 
cent solution of 
hydroquinon in 
tfie presence of 
0.2 gram of the 
specimens. 
Per cent. 
c. c. 
1 
0. 159 
19.1 
2 
.126 
15. 5 
3 
.098 
10.6 
