9 
which has become fluid and foul is more active as an ozone carrier 
than fresh blood. 
A critical study of the van Deen test was made by Liman (105) 
in 1863. According to this author when the spot or substance under 
examination gives a negative result with tincture or guaiacum and 
oil of turpentine, it can be said with certainty that it is not blood. 
When, however, a positive reaction is obtained — that is, when the 
spot or substance develops a blue color on the addition of these 
reagents — one can not be sure that it is blood without further inves- 
tigation, for the reason that many substances, such as iron salts and 
various organic materials, the vegetable gums, fresh roots, and the 
casein of milk, and tanned sheep leather, also give a blue color with 
guaiacum and oil of turpentine. 
So far as I have been able to discover. Day’s work (44, 45) con- 
sisted mainly in the repetition and verification of the earlier observa- 
tions of Schoenbein on the ox^^gen-cariwing power of blood. His 
method of carrving out Schoenbein’s blood test consisted in brushing 
over the spot with tincture of guaiacum and then pouring on the 
spot so treated an ethereal solution of h}nlrogen peroxide ; a beautiful 
blue color showed itself at once. On dark cloth he proceeded in the 
same manner, but after adding the reagents he pressed down on the 
cloth a sheet of white blotting paper, when each spot so treated 
gave a blue impression on the paper. In this way he succeeded in 
obtaining distinct tests for blood in certain cases when the microscopic 
examination had failed. 
The guaiacum test for blood was also thoroughly investigated by 
Ta}dor (184, 185, 186), his attention having been called to the test 
through the work of Day, who had succeeded in detecting blood on 
the clothes of a Chinaman under circumstances of great difficulty. 
In the course of his investigations Taylor pointed out the disadvan- 
tages of oil of turpentine as a reagent for the test, and employed in 
its stead first ozonized ether (a solution of hydrogen peroxide in 
ether) and later aqueous solutions of h^nlrogen peroxide. In this 
connection he found that hydrogen peroxide or a similar oxidizing 
agent is absolutely essential to the test, since the red coloring matter 
of blood, whether dissolved in water or alcohol, whether recent or of 
many years’ standing, whether from bird, fish, or reptile, does not 
render blue (oxidize) freshly precipitated guaiacum. In the presence 
of hydrogen peroxide, however, blood effects this change at once. 
He also called attention to the great solubility of the red-blood color- 
ing matter as one of its most distinguishing characteristics, and to 
the fact that blood ma}^ be distinguished from rust spots, from red 
dyes that have been fixed by mordants, and from red paint and from 
other red animal colors, by its great solubility. He found further 
that blood so dilute as to barely give a stain on white blotting paper 
178— Bull. 51—09 2 
