12 
preparation of the reagents required devolved upon the other party 
concerned in this investigation. By this arrangement it was hoped 
to secure greater accuracy than could otherwise be obtained. 
In collecting the samples of blood, the following mode of proce- 
dure was agreed upon and rigorously adhered to. In nearly all cases 
the samples of blood were obtained from the lobe of the ear. When 
this was impracticable, from the tip of the fore linger. The part was 
gently stroked for some time in order to flush it with blood. A deep 
stab was then made with a blood lancet and two samples collected, 
one for the hemoglobin determination, using a Dare hemoglobinome- 
ter; the second was carefully collected in a 1 cu. mm. blood pipette, 
which was then carefully washed out with a small amount of distilled 
water, and the sample made up to 5 c. c. with distilled water. The 
determination of the peroxidase activity of the second sample was 
then made as soon as possible; never after a longer interval than 
three hours, except in those cases where it was desired to deter- 
mine the effect of standing in contact with water on the peroxidase 
activity. The peroxidase activity of the several samples of blood was 
determined in the following manner: 
The solution of blood in 5 c. c. of water was carefully poured into 
a 250 c. c. measuring flask, the bottle washed, and the solution exactly 
made up to 250 c. c. with distilled water. 2 c. c. portions of this 
more dilute solution were then accurately measured out, using a form 
of pipette described bv Rosenau a in his work on the determination 
of the immunity unit for standardizing diphtheria antitoxin and 
which, for such work as this now under consideration, possesses many 
advantages in point of accuracy over the older method of using the 
pipette. These 2 c. c. portions of the blood solution (1 cu. mm. blood 
to 250 c. c.) were then mixed with 5 c. c. of a reagent containing the 
following substances: 0.032 grams phenolphthalin, 21 c. c. N/10 sodium 
hydroxide, 10 c. c. hydrogen peroxide, containing .031 grams H 2 0 2 
in 100 c. c., the whole made up to 100 c. c. with distilled water. The 
mixtures of blood solution and the reagent were then preserved 
in glass-stoppered bottles for the desired intervals, usually one 
to twenty-four hours. During this time the solutions acquired 
the purplish red color of phenolphthalein in alkali, and at the end of 
the given interval the amount of phenolphthalein produced as the result 
of the oxidation of the phenolphthalin was determined by comparing 
the color of the solution with that of a standard solution of phenol- 
phthalein in alkali containing 0.000318 grams of phenolphthalein, 
and 1 c. c. N 10 sodium hydroxide at a total dilution of 7 c. c. The 
color comparisons were made in a Duboscq-Pellin colorimeter, the 
readings being made in diffused light. 
a Bulletin 21, Hygienic Laboratory, April, 1905, fig. 13, p. 64. 
