22 
THE VALUE OF THE GUAIACUM TEST AND SIMILAR REACTIONS. 
It is evident from the foregoing that a considerable number of 
substances other than blood show the guaiacum reaction, or similar 
reactions with other cbromogenic substances, either alone or in the 
presence of a peroxide. That such is the case has given rise to the 
most vddely differing opinions as to the general utility of these tests 
in hematologic work and in forensic investigations. Thus, according 
to Alsberg (3) the guaiacum test for blood is unsatisfactory. Accord- 
ing to Bell (15) the test is beautiful, but can not be relied on as posi- 
tive proof of the presence of blood, and according to Breteau (25) 
the van Deen reaction should be handled with great circumspection. 
Woods (206) is of the opinion that the chief value of the guaiacum 
reaction is as a preliminary test, and Whitney (203) holds that the prin- 
cipal value of the guaiacum and aloin tests for blood is that if a speci- 
men under examination gives no reaction with these substances then 
blood is absent. In other words, the principal value of such tests 
lies m the negative findings. On the other hand, according to 
Buckmaster (29), the guaiacum test, when properly carried out on 
boiled solutions, is a delicate reaction for blood, and according to 
Florence (54) also, it is a valuable reaction. Hemphill (67) also 
regards it as the most elegant and delicate of the chemical tests for 
blood. According to Jenne (76) the guaiacum and hematin tests are 
the most simple and generally employed. He calls attention to 
the well-known fallacies of the reaction, and recommends the proper 
control of the reaction by testing all of the reagents employed, and 
states that when these fallacies have been eliminated and the test 
cautiously apphed and a blue color obtained the stain certainly con- 
tams blood. Fahrner (52) regards the test as specific for blood m 
spite of all objections which have been urged against it, and that so 
far as its practical signihcance is concerned, excluding certain possible 
errors, fresh tincture of guaiacum with old oil of turpentine is a re- 
agent for blood. Accorchng to Weber (201) van Deen’s reaction as 
applied to the acetic acid-ether extract of feces is a test of delicacy 
and reliability, and according to Schumm (160) with certam precau- 
tions the test is applicable to blood and is trustworthy. Maille, 
Mayet, Lefort, and Cornil (116) have arrived at the conclusion that 
the guaiacum test is always useful, especially if the findings are nega- 
tive, and according to Palleske (123) if the guaiacum test fails it is 
absolutely certain that no blood can be present, whereas if it gives a 
positive result it indicates that blood is probably present, but the 
test must' be confirmed. Siefert (170) is of the opinion that the 
guaiacum test enables one to arrive at a more than approximate 
conclusion, a negative result certainly indicating the absence of 
blood, and in case the substance under examination yields a blue 
