1 cu. mm. to 250 c. c., can oxidize 38.5 per cent of the phenolphthalin 
present in one hour; whereas blood alone, at a dilution of 1 c. mm. to 
100 c. c. acting in the presence of alkali, is only able to oxidize 4.6 
per cent of the phenolphthalin in the same time. When hydrogen 
peroxide is present the maximum of oxidation is reached in one hour; 
after twenty-four 
hours. 
Secondl} 7 , as already pointed out in the foregoing, it is evident that 
when blood alone is employed to effect the oxidation of the phenol- 
phthaliu the depth and intensity of the phenolphthalein color persists 
unchanged for a much longer time than when hydrogen peroxide is 
present. For example, with normal blood the color remains undimin- 
ished for seventy-two hours or even longer; whereas with the blood 
of diseased persons the fading takes place somewhat more rapidly. 
On the other hand, it will be recalled in this connection that when 
hydrogen peroxide is present the color of the phenolphthalein fades 
considerably, even in twenty-four hours, and, in fact, often in even 
less time. Hence, as already 7 pointed out, it would seem that one of 
the causes of the fading of the phenolphthalein color is the presence 
of hydrogen peroxide. 
Another point of interest in this connection and one that requires 
still further investigation is that in no case here studied, either with 
or without hydrogen peroxide, is the phenolphthalin completely oxi- 
dized, the maximum oxidation with blood alone being 66.9 per cent 
and with blood and hydrogen peroxide 47.6 per cent. This either 
indicates an insufficiency in available oxygen or it ma} 7 be associated 
with the fading of the phenolphthalein color. 
Thirdly, it will be observed that the direct oxidizing power of the 
blood of fifteen persons has been determined for twenty -four hours. 
In the last column of the table will be found the oxidizing power of 
these several specimens of blood calculated in terms of normal blood 
(viz, that of Amoss), arbitrarily made equal to 100. A comparison 
of these numbers among themselves and with the percentages of hemo- 
globin of the several specimens reveals much the same relationship 
that has been found to exist between peroxidase activit} 7 and per cent 
of hemoglobin, viz, the former is proportionate to the quantity of 
hemoglobin present in blood. So here the higher the hemoglobin 
content the greater the direct oxidizing power of blood. Out of the 
fifteen specimens whose direct oxidizing power has been determined 
eight have been found to contain hemoglobin varying from 83 to 99, 
and eleven have been found to have a direct oxidizing power varying 
from 85 to 107. Four of these bloods were markedly low in percent- 
age of hemoglobin, the quantity varying from 35 to 54 per cent 
and three have been found to have a low direct oxidizing power 
varying from 43 to 67. 
whereas in blood alone the maximum is reached only 
