42 
of stomach contents we were able to detect 1 part of blood in 1,750 
parts of the stomach contents. In ordinaiy clinical work it is not 
Hkelv that any attention woidd be paid to quantities of blood smaller 
than this, and hence no attempts have been made to recognize 
smaller quantities. I have no doubt, however, that by the use of 
aluminium hydroxide and the pbenolpbtbalin reagent, much smaller 
quantities of blood could be detected in gastric contents. 
Reference has been made to a recent communication by Fozzi- 
Escot (128) on the use of pbenolpbtbalin as a reagent for blood, in 
which be severely criticises the work of Delearde and A. Benoit (16) 
on this subject, and seems inclined to doubt the usefulness of this sub- 
stance both as a test for blood and as a reagent for the oxidases. As 
a matter of fact, however, since this compound was first proposed by 
Kastle and Sbedd (S3) as a reagent for the oxidases it has given excel- 
lent results, both in the bands of Kastle and other cbenfists, and has 
proven especially valuable in recent investigations on the peroxi- 
dases. In my opinion, therefore, these adverse criticisms of this 
reagent on the part of Pozzi-Escot, for the work for which it has 
thus far been employed, are absolutely unjustifiable in the light of 
the facts, and it is a subject which can not be dismissed on the basis 
of a few faulty obseiwations. As a matter of fact, phenolphthalin 
is not only a beautifid reagent for the oxidases and peroxidases, but 
it lends itself admirably to quantitative investigations in this field, 
since the product of the oxidation — phenolphthalein — is of perfectly 
definite composition and can be determined colorimetrically with 
great accuracy. This can certainly not be said of a great many 
substances which have been used in work of this kind. Further, 
that it is a valuable reagent for blood can scarcely be doubted. 
According to Pozzi-Escot (128) an alkaline solution of phenolphthalin 
containing hydrogen peroxide is valueless as a reagent for blood for 
the reason that it ^fields phenolphthalem with the following sub- 
stances besides blood, viz, extract of malt, saliva, ash of blood, pus, 
the greater number of organic secretions, plant extracts, certain 
urines absolutely free from blood, and a great number of metalic salts, 
such as those of cobalt, manganese, iron, lead, etc. These obseiwa- 
tions do not agree with our own experience for at least che greater 
number of these substances. In order to determine to precisely 
what extent his criticisms are justified, however, I have recently 
tested the conduct of sahva, extract of malt, potato peel, horse- 
radish, human blood, and copper sulfate towards the followmg 
phenolphthalin reagents : 
1. The oxidase reagent, containing 0.032 gram of phenolphthalin, with 1 c. c. 
X 10 sodium hydroxide, made up wi^h distilled water to 100 c. c. 
2. Alkaline phenolphthalin, containing 0.032 gram of phenolphthalin, with 21 
c. c. of X 10 sodium hydroxide, made up with distilled water to 100 c. c. 
