280 THE AMERICAN MONTHLY [Sept 



the numerous compounds which, as, for instance, nitrous 

 acid, free chlorine, bromine and iodine, chromic anhyd- 

 ride permanganic acid, peroxide of lead, the ferric and 

 cupric salts, quinone, etc., directly color blue the guaia- 

 cum resin ; because first of all, many of these bodies are 

 exempted a priori in the majority of materials submitted 

 to the blood-tests, and secondly, because in their pres- 

 ence the liquid extract of a stain to be tested for blood 

 would at once strike a blue color when mixed with a lit- 

 tle guaiacum tincture before the addition of Hunef eld's 

 peroxide-solution. In regard to these facts, the somewhat 

 superficial notice of some text-books, viz., that the guaia- 

 cum blood-test is not reliable, "because many substances 

 change guaiacum for themselves," cannot be taken as a 

 warning against the use of the said method, since, cer- 

 tainly, no careful analyst will ever neglect to avoid mis- 

 takes by availing himself of the control-reactions indi- 

 cated in each case! Yet, such substances of inorganic or 

 organic origin, as share the "ozone-transferring" quality 

 with the contents of the blood cells, viz., the coloring 

 matter of blood, might in some single cases lead to a false 

 interpretation of the guaiacum-blue-reaction. Among or- 

 ganic vegetable substances, bodies of the class of fer- 

 ments may be named, as well as hydrolytic ferments 

 (enzymes in the stricter sense of the word) chiefly so- 

 called oxidizing ferments, as they occur in numerous parts 

 of plants, especially in mushrooms and plant seeds, while 

 among animal substances in the first line saliva, extracts 

 of some organs, the contents of white blood cells and pus 

 cells, etc., show analogous properties. These albuminous 

 substances of the character of ferments, existing in vege- 

 table and animal cells, and exerting in a more or less 

 manifest degree a catalytic and, at the same time "oxy- 

 gen-transferring" action towards hydric peroxide, strictly 

 differ from the coloring matter of blood in that the last- 

 named action is cancelled, or at least most strikingly 



