35 
TESTING FOR BLOOD IN PATHOLOGICAL FLUIDS AND 
SECRETIONS. 
The fact that animal tissues in many cases retard the oxidation 
of phenolphthalin under the influence of blood indicates that the 
testing for blood in various animal tissues and secretions under 
normal and pathological conditions is altogether a different matter 
from testing for blood in pure aqueous solutions, and that the 
delicacy of such tests is very likely to be interfered with. As a 
matter of fact, strictly chemical tests for blood such as the guaiacum 
test have been more extensively used for the recognition of blood 
stains than in the examination of body fluids for blood. (See 
Wittstein, 204, and also Schuster, 165.) Our attention was first 
directed to this phase of the subject through the study of the per- 
oxidase reaction of certain normal and pathologic urines. In the 
presence of hydrogen peroxide and phenolphthalin certain urines' 
containing blood gradually developed a deep blood-red color, after 
the addition of N/10 sodium hydroxide, due to the production of 
phenolphthalein, whereas other urines known to contain blood failed 
entirely to show this change of color. Evidently, therefore, certain 
urines contain substances which retard the oxidation of phenol- 
phthalin by blood and hydrogen peroxide. Similar difficulties have 
been encountered by other observers, and in no instance has a method 
of blood testing been devised which will recognize in urine, feces, 
gastric contents, etc., as small an amount of blood as can be detected 
in water. 
THE ADSORPTION OF BLOOD PIGMENTS BY VARIOUS COLLOIDAL 
AND FINELY DIVIDED SUBSTANCES. 
The attempt has been made to overcome the difficulty in testing 
for blood in pathologic fluids and secretions referred to above by 
treating the urine or other fluid with a substance which would absorb 
the blood pigment and leave the interfering substances in solution. 
The earliest observations in this field were made by Rose (134), 
who found that such substances as aluminium hydroxide, ferric 
hydroxide, etc., have the power of adsorbing blood coloring matters 
from their aqueous solutions. These observations have been con- 
firmed by Fleming (53). Later Struve (177) made use of tannin 
for this purpose, and other observers, among them Dragendorf (48), 
Schwartz (167), Berg (17), have employed zinc acetate for this pur- 
pose, and still others, among them Bird (20), and Klein (87), have 
used a mixture of tannin and zinc acetate. Heller has also proposed 
a test for blood in urine which depends upon the fact that the earthy 
phosphates of urine precipitated on warming with alkali have the 
power of absorbing any blood-coloring matter which the urine may 
contain, in consequence of which the precipitate takes on^ pink or 
