446 LECTURE XIX. 



present, both in the animal and vegetable kingdoms. It is easy to detect 

 their presence by means of certain chemical reagents. If, for example, 

 an organ extract is shaken with an alkaline solution of a-naphthol plus 

 p-phenylenediamine, the formation of blue indophenol is soon apparent. 1 

 Without the addition of the organ extract, the formation of this color 

 takes place very much more slowly. A reaction made use of by Schonbein 

 is the blue color obtained with tincture of guaiacum. Its indication of the 

 presence of oxidizing ferments is, however, not altogether reliable. The 

 guaiacum reaction is also brought about by the presence of numerous other 

 oxidizing agents, such as ferric chloride, chromic acid, chlorine, bromine, 

 etc. By means of these organ extracts salicylic acid may be converted 

 into benzoic acid, and benzyl alcohol into benzoic acid. 2 Formaldehyde 

 is similarly converted into formic acid, 3 and arsenious acid into arsenic 

 acid. 4 a-naphtylamine is changed into violet-blue oxynaphtylamine, and 

 benzidine into a brownish-violet substance. 5 Likewise phenolphtalin is 

 changed to phenolphthalein. 6 These are a few examples of the oxida- 

 tions which may be brought about readily by means of organ-decoction or 

 organ-extract; and, in fact, with plants the oxidizing action of certain of 

 their organs, the roots for example, may be demonstrated directly by 

 allowing them to grow upon strips of paper moistened with solutions of 

 the above-mentioned reagents. 



By means of these discoveries, the whole question of animal and vege- 

 table oxidations, the latter not differing from the former in its essential 

 particulars, has been turned in an entirely new direction. Although, 

 at the present stage of its development, it is perhaps going too far to speak 

 of a perfect explanation of the oxidation processes in the tissues, still, on 

 the other hand, it is true that numerous processes which would be other- 

 wise beyond our comprehension, are now better understood. As we shall 

 see later, we have every reason to believe that a given ferment always acts 

 upon only quite definite compounds. Thus the proteolytic ferment, tryp- 

 sin, attacks only proteins, and not carbohydrates. It might have been 

 assumed a priori, that the oxidizing ferments are exceptions in this respect, 

 and are in general capable of serving as carriers of oxygen. This is, as a 

 matter of fact, not the case, as we know from numerous observations. 

 Thus it is only certain definite oxidizing ferments which are capable of 

 causing the above-mentioned oxidation of a-naphthol and p-phenylene- 

 diamine to indophenol in alkaline solution. In the liver, for example, 



F. Rohmann und W. Spitzer: Ber. 28, 567 (1895). 



Jaquet: Arch, exper. Path. Pharm. 29, 386 (1892). 



Pohl: ibid, 38, 65 (1896). 



W. Spitzer: Pfliiger's Arch. 71, 596 (1898). 



M. Raciborski: Anzeiger der akad. der Wissensch. zu Kraukau, 1905, 338. 



Kastle and Shedd: Am. Chem. J. 26, 527 (1901). 



