. EXAMINATION OF BLOOD. 49 



the blood-pigment or blood-corpuscles. But the reaction 

 may be shown very beautifully if we allow a few drops of 

 violet-red litmus tincture to soak into a porous clay plate, 

 and then place upon this spot a drop of blood and wash it 

 off at once. There is thus obtained a distinct, even intensely 

 blue spot (Liebreich). But even with ordinary litmus paper 

 the alkaline reaction may be shown in the following manner: 

 Grind some blood in a mortar with an excess of powdered 

 ammonium sulphate, so that even after long grinding a por- 

 tion of the salt still remains undissolved. Into this paste 

 dip a rather wide strip of red litmus paper and then wash it 

 off thoroughly with water. Zuntz recommends litmus paper 

 made out of tissue-paper. Moisten this with a concentrated 

 solution of salt or sodium sulphate or magnesium sulphate, 

 place a small drop of blood on the paper with a glass rod, and 

 absorb the liquid at once with blotting-paper. 



II. Conduct towards Guaiacum and Oil of Turpentine. 



To 8 or 10 cc. of water add a few drops of blood (shaking 

 thoroughly), then some tincture of guaiacum (freshly pre- 

 pared by dissolving some gum guaiacum in alcohol in a test- 

 tube) till the solution becomes milky, and finally some oil of 

 turpentine which has stood for some time. On shaking, the 

 mixture becomes intensely blue (oxidation of the gum guaia- 

 cum: the blood-corpuscles act as carriers of oxygen from the 

 ozonized oil of turpentine to the gum guaiacum). 



III. Reaction with Hydrogen Peroxide. 



To a few cubic centimeters of blood add several times the 

 volume of a solution of hydrogen peroxide: marked frothing 

 due to the escape of oxygen (so-called catalytic action of the 

 blood-pigment). 



