ii PRIMARY DISSOCIATION-PRODUCTS 53 



formation of indican, while tryptophane prepared by the method of 

 Hopkins and Cole on being injected into the larger intestine invari- 

 ably led to the appearance of indican in the urine. He therefore 

 comes to the conclusion that tryptophane cannot be a skatol-compound, 

 but must be an indol-derivative, and Ellinger x has proved by synthetic 

 work that Salkowski's acid is really not a skatol-carboxylic acid, but 

 an indol-acetic acid. 



CH 3 A CH 2 .COOH 



C, 



>C . COOH 



N/ 



H V H 



Skatol-carboxylic acid. Indol-acetic acid. 



Either of these alternative constitutions will explain the yield of 

 skatol and C0 2 on putrefaction. Now, skatol-carboxylic acid being 

 recognised as indol-acetic acid, it is clear that ' skatol-acetic ' must be 

 indol-propionic acid, and therefore tryptophane an indol-amino-propionic 

 acid. Ellinger 2 has also found that Hopkin's tryptophane, fed to 

 dogs, gives kynurenic acid in the urine, a fact which inclines him to 

 ascribe to it the constitution of indol-^-amino-propionic acid. 



COOH 



-C^-CH CH 2 (NH 2 ) 

 /CH 



CH 



. CH(NH 2 )COOH 



N' 



H V H 



Tryptophane (Ellinger). Tryptophane (Hopkins). 



Ellinger's formula Avould further explain the tendency towards the 

 closure of the pyridin-ring in tryptophane, and would make the 

 assumption of a pyridin-nucleus in the albumin-molecule 3 superfluous, 

 a view which was based on the fact that melanoidins form pyridin on 

 being reduced (Samuely). 4 According to Ellinger a genetic relation- 

 ship exists between tryptophane and many of the pyridin and quinoline 

 derivatives in plants. 



Hopkins 5 thinks it unlikely that Ellinger's view is correct, because 



1 Alexander Ellinger, Ber. d. deutsch. chem. Gesellsch. 37. 1801 (1904). * 



2 Alexander Ellinger, Zeitschr. f. physiol. Chem. 43. 325 (1904). 

 a Hofmeister, Ergebnisse d. Physiol. 1. 768 (1902). 



4 Samuely, Hofmeister s Beitr. 2. 355 (1902). 



5 Hopkins, private communication, January 1905. 



