10 
admits of detection by the guaiacum test. He was also able to detect 
it in from 1 to 2 dram portions of a solution containing 1 drop of 
blood in 8 ounces (240 c. c.) of water. These small amounts, he 
says, are far beyond recognition by the ordinar}^ chemical tests. 
He was also able to detect blood on a towel two years after the spot 
was produced. He observed further that hemin crystals also acquire 
a blue color when treated with h 3 vlrogen peroxide and guaiacum. 
He also investigated the conduct of a large number of substances 
tov’ard guaiacum alone and toward guaiacum containmg hydrogen 
peroxide. Among the inorganic substances which he found to blue 
guaiacum directly are potassium manganate and permanganate, lead 
and manganese peroxides, and, in the presence of water, solutions of 
chlorine, bromine, iodine, h}q3onitrous acid, h^^pochlorites, the per- 
salts of iron, potassium ferro- and ferri-cy ankles, and platinum black, 
and among organic substances, gums — such as gum acacia — gl ten, 
unboiled milk, raw potato, the juices of many fresh roots, certain 
inks, and certain kinds of white leather. On the other hand, starch, 
fibrin, and boiled milk have no effect upon it. He observed further 
that heat destroys the power of these vegetable substances to blue 
guaiacum, and that with ordinary fruit stains, cochineal, and iron rust, 
guaiacum gives no test. He points out that with some solutions of 
hydrogen peroxide guaiacum gives a blue color in the absence of 
blood and similar carriers, probably for the reason that such solu- 
tions contain hydroclfioric acid containing traces of ferric salts, and 
that certain old tinctures of guaiacum give a blue color with blood 
without the addition of hydrogen peroxide. He therefore calls 
attention to the necessity of selecting unoxidized pieces of guaiacum 
from the central portions of the lumps of resin for medicolegal 
work. 
Finally, he calls attention to the injustice which has been done 
to the Van Deen test by medicolegal writers, some of whom have 
pronounced the guaiacum test untrustworthy for the reason that 
other substances impart the blue color to guaiacum. He points out 
that while this statement is true, it does not conve}^ the whole truth; 
and he himself is of the opinion that the use of guaiacum adds another' 
and valuable chemical test to those hitherto emplo^^ed for the detec- 
tion of blood. It enables the chemist to detect it with reasonable 
certainty when it is present in very small quantities, or to trace it in 
those cases in which an attempt has been made to remove it by 
washmg; and when the result of the test is negative, it enables him 
to say that the suspected stain was not caused by blood, a fact of con- 
siderable importance in medicolegal inquiries. 
As may be seen from the bibliography given at the end of this 
article, these and similar reactions for blood have formed the subject 
of a large number of investigations. It is impossible to include 
