DETECTION OF PEROXIDASES 539 



the blue color was used as a blood test by shaking the speci- 

 men up in tincture of guaiac and old oil of turpentine. The 

 action of the turpentine in this latter depends upon the inci- 

 dental and inconstant presence of peroxides in it, developing 

 especially in the formation of resin. 5 



Iodine Reaction. In the detection of peroxidases in ani- 

 mal tissues the frequently employed iodine reaction of Bach 

 and Chodat seemed to Czyhlarz and the author a fairly suited 

 method (separation of iodine from acidulated iodide of 

 potassium solution in the presence of hydrogen peroxide and 

 detection of the liberated iodine by means of starch paste) , 

 in that (in differentiation from the oxidation of guaiaconic 

 acid and other cyclic chromogens) the oxidation of hydriodic 

 acid was not catalytically accelerated by haemoglobin in the 

 experiment conditions employed by the writers. They were 

 able by this method to establish the presence of true per- 

 oxidases in leucocytes (pus cells), lymphoid tissue (bone 

 marrow, spleen, lymph nodes), and in sperm. They em- 

 phasize the point, however, that the test can be regarded as 

 conclusive only when the reaction is positive, not when it 

 is negative, because of the impossibility of excluding inhibi- 

 tion of the reaction by albumins and other iodine-fixing tissue 

 constitutents. As a matter of fact, J. Wolff and E. de Stoklin 

 have been able to show that oxyhsemoglobin (present, of 

 course, in all tissues) under certain changes of experimental 

 conditions will also behave quite like a vegetable peroxidase 

 toward iodide of potassium and hydrogen peroxide, if care 

 is taken to immediately remove any excessive iodine. 6 Ac- 

 cording to F. Battelli and Lina Stern this is also true if 

 in arranging the reaction hydrogen peroxide is replaced by 

 ethylhydroperoxide ; although it is at present impossible 

 to say what is the cause of the difference of behavior of the 

 haemoglobin to the two peroxides. The authors just re- 



5 Cf. B. Moore and E. Whitley, Biochem. Jour., 4, 136, 1909. 

 8 J. Wolff and E. de Stocklin (Instit. Pasteur, Paris), Ann. Instit. Pasteur, 

 25, 319, 1911. 



