ARNOLD'S REACTION 135 



from the preliminary findings it was held that the alkyl was 

 really present in the form of trimethylamine. In conformity 

 with the above the amount of trimethylamine recoverable by 

 distillation from normal fresh urine was found extremely 

 small. And, too, expectation of obtaining larger amounts 

 after acid or alkaline hydrolysis was not fulfilled. Somewhat 

 larger amounts of the base were found in spoiled urines; 

 and the largest proportions (about 3 to 6 centigrams in 

 the liter of urine) were met in a few urines which, with or 

 without addition of toluol, had been standing for a long 

 time at room temperature, from which it must be inferred 

 that the cleavage production of trimethylamine is the result 

 of a fermentative process acting on some "mother sub- 

 stance. ' ' Doubtless the physiological significance of the ap- 

 pearance of trimethylamine in urine has been much over- 

 estimated by the earlier investigators. 47 



Arnold's Reaction. One more peculiar substance should 

 be mentioned, which appears in the urine particularly after 

 ingestion of meat or meat bouillon and which underlies the 

 6 ' Arnold reaction. ' ' Upon addition of sodium nitroprusside 

 and alkali a violet color is assumed, which changes to blue 

 when acetic acid is added. The nature of this reaction is 

 not known; and the substance producing it is, to say the 

 least, very fugitive, disappearing from the urine in the 

 course of a few days, even if the specimen be preserved by 

 addition of sublimate. It has been stated that the reaction 

 is a "typical meat reaction, " but this probably cannot be 

 maintained as it has also been observed after use of milk, 

 cheese and eggs. 48 



47 C. Serena and A. Percival, Jahresber. f. Tierchem., 29, 338, 1890; F. de 

 Filippi, Zeitschr. f. physiol. Chem., 49, 433, 1906. 



48 V. Arnold (Lemberg), Zeitschr. f. physiol. Chem., 49, 397, 1906; Th. 

 Holobut (Lemberg), ibid., 56, 117, 1908; X. Buss, Inaug. Dissert., Zurich, 

 1910, cited in Centralbl. f. d. ges. Biol., 11, No. 1702; J. Caretti, Bull. Scienze 

 Med., 80, 253, 1909. 



