DETECTION OF BLOOD 545 



tissues complex iron compounds which may be capable of 

 conveying oxygen; the haemoglobin is to be regarded as a 

 compound of bivalent iron with an additional valence open 

 for a loose attachment 20 (vide infra, Chapter XXIV). 



The blue respiratory coloring matter of the Crustacea 

 and mollusks, h&mocyanin (Vol. I of this series, p. 224, 

 Chemistry of the Tissues) also manifests peroxidase reac- 

 tions in a striking way, here apparently related with the 

 copper it contains. 21 



Chemico-Legal Detection of Blood by Means of Per- 

 oxidase Reactions. Brief attention may be given to a 

 practical phase of the peroxidase problem, the application 

 of the peroxidase reactions of haemoglobin to the chemical 

 detection of blood for legal purposes. For this purpose, in 

 addition to those methods which are based on a specific char- 

 acteristic of blood coloring matter (as spectroscopic detec- 

 tion, or the demonstration of Teichmann's crystals), con- 

 siderable use has been made of the peroxidase reactions, that 

 is, of the colors which solutions of guaiac resin or guaiaconic 

 acid, aloin, phenolphthalin, leukomalachite-green, benzidin, 

 etc., assume in contact with hydrogen peroxide and blood. 

 The marked sensitiveness of these reactions has led to their 

 frequent use in the examination of drops of blood on cloth- 

 ing, walls and utensils ; but the value of evidence thus ob- 

 tained has been restricted before courts particularly because 

 of the fact that there are a great many other substances 

 which possess the power of conveying oxygen just as haemo- 

 globin does, as for example rust, a number of iron- and cop- 

 per-compounds, oxide of lead, manganese oxide, chlorine, 

 bromine, iodine, and, too, organic substances of all sorts as 

 pus, saliva, milk, sweat and many vegetable materials. 22 



20 W. Madelung (Heidelberg), Zeitschr. f. physiol. Chem., 71, 204, 1911. 



M C. L. Alsberg, Arch. f. exper. Pathol: Schmiedeberg's Festschr., p. 40, 

 1908; C. Fleig, C. R. Soc. de Biol., 69, 66, 110, 1910. 



22 Literature of Legal Examination of Blood: O. Leers, Die forensische 

 Blutuntersuchung, Berlin, J. Springer, 1910; cf. also O. Schumm and E. 

 Westphal ( Hamburg-Eppendorf ) , Zeitschr. f. physiol. Chem., 46, 510, 1905. 

 35 



