CASUAL URINARY CONSTITUENTS. 737 



The fact that benzene may be oxidized outside of the body into caibon 

 dioxide, oxalic acid, and volatile fatty acids has been known for a long 

 time; and as in these cases a rupture of the benzene ring must take place, 

 so also, it must be admitted, when aromatic substances undergo a com- 

 bustion in the animal body, a splitting of the benzene nucleus with the 

 formation of fatty bodies must be the result. If this does not occur, then 

 the benzene nucleus is eliminated with the urine as an aromatic compound 

 of one kind or another. As the benzene nucleus can protect a substance 

 belonging to the fatty series from destruction when conjugated with it, 

 which is the case with the glycocoll of hippuric acid, it seems that the 

 aromatic nucleus itself may likewise be protected from oxidation in the 

 organism by synthesis with other bodies. The aromatic ethereal-sul- 

 phuric acids are examples of this kind. 



The difficulty in deciding whether the benzene ring itself is destroyed 

 in the body lies in the face that we do not know all the different aromatic 

 transformation products which may be produced by the introduction of 

 any such substance into the organism, and which must be sought for in 

 the urine. On this account it is also impossible to learn by exact quanti- 

 tative determinations whether or not an aromatic substance ingested or 

 absorbed appears again unchanged in the urine. Certain observations 

 render it probable that the benzene ring, as above mentioned, is at least 

 in certain cases destroyed in the body. SCHOTTEN, BAUMANN, and others 

 have found that certain amino-acids, such as phenylamino-propionic 

 acid, amino-cinnamic acid, and tyrosine, when introduced into the body 

 cause no increase in the quantity of known aromatic substances in the 

 urine; this makes a destruction of these amino-acids in the animal body 

 seem probable. According to F. KNOOP 1 phenyl-a-lactic acid and 

 phenyl-a-ketopropionic acid (phenyl pyroracemic acid) have a similar 

 behavior. According to Ju YALTA and PORCHER phthalic acid is also 

 burnt in the animal body. The last investigator found that the three 

 phthalic acids have varying effects, as the o-acid is almost completely 

 burnt in dogs, while about 75 per cent of the m- and p- acids are excreted 

 unconsumed. This corresponds with the rule found by R. CoHN, 2 that 

 among the di-derivatives of benzene the ortho-compounds are more 

 readily destroyed than the corresponding meta- and para-compounds. 

 The claims of .Tu YALTA and PORCHER are unfortunately disputed by 

 PRIBRAM and PoHL. 3 



1 Schotten, Zeitschr. f. physiol. Chem., 7 and 8; Baumann, ibid., 10, 130. In regard 

 to the behavior of tyrosine, see especially Blendermann, ibid., 6; Schotten, ibid., 7; 

 Bass, ibid., 11: and R. Cohn, ibid., 14; F. Knoop, Der Abbau aromatischer Fett- 

 sauren ini Tierkorper, Habilit.-Schrift, Freiburg, 1904. 



2 Zeitschr. f. physiol. Chem., 17. 



3 Juvalta, Zeitschr. f. physiol. Chem., 13; Pribram, Arch. f. exp. Path. u. Pharm., 

 51; Porcher, Bioch. Zeitschr., 14; Pohl, ibid., 16. 



