32 
each of the blood solutions. The tubes containing these substances 
were allowed to stand twenty-four hours at ordinary temperature, 
at the end of which time they were compared in the Duboscq colorim- 
eter with a fresh standard of phenolphthalein in alkali containing 
0.0318 gram of phenolphthalein in 21 c. c. of X 10 sodium hydroxide 
and sufficient water to bring the total volume of the solution up to 
100 c. c. The following are the results of these comparisons: 
Concentration 1. 0 0. 5 0. 2 0. 1 
Scale reading 5 1.1 2.3 5.2 
The standard was set at 0.2 division on the scale of the colorimeter. 
It is evident from these results that the oxygen-carrying power of 
blood towards an alkaline solution of phenolphthalin containing 
hydrogen peroxide and its oxidizing power toward alkaline phenol- 
phthalin alone, is directly proportional to the concentration of the 
blood. 
In my opinion, two things are necessary for the more exact deter- 
mination of hemoglobin than is possible with the instruments now 
in use for this purpose : first, to weigh the blood used in the determina- 
tion instead of attempting to measure such a viscous licjuid in pipettes 
of such narrow caliber as are ordinarily employed in hematologic 
work, and, second, to use a colorimetric method depending on the 
oxidation of phenolphthalin by blood, whereby a coloring matter 
of great intensity of color is obtained. I hope, therefore, at some 
ftiture time to work out the details of a method for the exact deter- 
mination of hemoglobin based on these principles. 
ON THE EFFECT OF VARIOUS ANIMAL TISSUES ON THE OXIDA- 
TION OF ALKALINE PHENOLPHTHALIN BY BLOOD ALONE AND 
IN THE PRESENCE OF HYDROGEN PEROXIDE. 
It soon became apparent in the course of this investigation that 
the oxidation of phenolphthalin in alkaline solution by blood alone 
and in the presence of lyvdrogen peroxide was considerably retarded 
by extracts of various animal tissues. In order to determine to what 
extent this occurred, the following experiments were carried out: 
A guinea pig was anesthetized and killed by bleeding, and a solution 
of the pig’s blood was prepared by dissolving 0.0225 gram of the 
blood in 250 c. c. of water. This was labeled solution Xo. (1). After 
the death of the animal the following tissues were removed and 
labeled as indicated: Liver, (2): bone marrow, (3\: pancreas, (4); 
spleen, (5): muscle, (6): lung, (7); suprarenals, (S): brain, (9). 
One-tenth gram of each of these tissues was rubbed up in a mortar 
with 10 c. c. of blood solution Xo. (1) and the several solutions num- 
bered to correspond with the numbers of the tissues used. These 
solutions were then compared in oxidizing power with the blood 
solution towards the alkaline phenolphthalin containing hydrogen 
