778 URINE. 



amyl alcohol yielded relatively large quantities. Secondary alcohols 

 produced conjugated glucuronic acids, and indeed to a greater extent than 

 the primary alcohols, especially in rabbits. The ketones are reduced in 

 part into secondary alcohols and are partly excreted as the conjugated 

 acid. This could be shown for acetone with rabbits but not with dogs. 



The homo- and heterocyclic compounds pass, as far as is known, 

 into the urine as such, or after a previous partial oxidation or synthesis 

 with other bodies, and appear as so-called aromatic compounds. This 

 applies at least to foreign substances that are introduced into the body. 



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

 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. The manner in which this benzene ring is opened 

 is not known. Still JAFF l has detected muconic acid in the urine of 

 dogs and rabbits which had been fed for a long time with benzene, and 

 suggest one way in which the benzene can be split in the animal body. 



CH CH 



HC X CH HC X COOH 



| 1 1 | . That the demolition of the benzene nucleus 



HC CH HC COOH 



CH CH 



occurs in certain cases, as in tyrosine and phenylalanine according to 

 the present view, over homogentisic acid, has already been mentioned. 

 The most striking example of a complete combustion of the benzene 

 nucleus is given by tyrosine, which as previously mentioned (page 737) 

 can be absorbed even in large quantities and decomposed without the 

 observer being able to detect any of the cleavage products of it in the urine. 

 Other examples of readily and at least in greatest part combustible aroma- 

 tic substances are phenyl-a-lactic acid, p-oxyphenylpyruvic acid and a-amino 

 cinnamic acid. According to JUVALTA 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 



1 Zeitschr. f. physiol. Chem., 62. 

 s Ibid., 17. 



