62 CHEMISTRY OF THE PROTEIDS CHAP. 



sociated in the body as they are normally, but appear almost quanti- 

 tatively and completely unaltered in the urine. The behaviour of the 

 two cystins when administered to a person suffering from cystinuria 

 is especially interesting, because such a person reacts to the isomeric 

 stone-cystein, as does a healthy individual to protein-cystin, i.e. the 

 cystin disappears completely as such, there being eliminated a corre- 

 sponding amount of sulphates and thiosulphates. If protein-cystin 

 be given to a patient suffering from cystinuria, then this cystin is 

 excreted as such in addition to the amount of protein-cystin normally 

 excreted. 



While mono-amino-acids appear in the urine when given to a cystin- 

 uric person, di-amino-acids behave quite differently, thus lysin gives 

 rise to cadaverin and arginin gives rise to putrescin. We are dealing 

 here with the first known fermentative process by which C0 2 is 

 split off. 



Lysin CH 2 . NH 2 (CH 2 ) 3 CH . NH 2 . COOH = 



CH 2 . NH 2 (CH 2 ) 3 CH 2 . NH 2 or pentamethylene-diamine. 



In the case of arginin there is also liberated cyanamide or a urea- 

 remainder : 



NH 2 . C(NH) . NH_ CH 2 (CH 2 ) 2 CH . NH 9 COOH = 

 NH 2 CN + C0 2 + NH 2 CH 2 (CH 2 ) 2 CH 2 . NH 2 . 



These observations of Loewy and Neuberg 1 are a complete confirma 

 tion of the results which Ellinger 2 obtained in the test tube. 



The ratio of the sulphur taken in the food to that excreted in 

 the bile has been especially investigated by Kunkel, 3 Spiro, 4 and 

 Bergmann. 5 The last mentioned determined in the dog the amount 

 of sulphur eliminated in the bile as taurin after the administration 

 of cystin mixed with a diet in other respects constant. As long as 

 onlv cystin was given no increase in the amount of taurin could be 

 observed, but as soon as sodium glycocholate as well as cystin was fed, 

 then an increase in taurocholate took place. He explains this result 

 by assuming that cystin is converted into taurin in the body, but that 

 the dog could not form the requisite amount of cholalic acid to enable 

 it to synthetise taurocholates. 



Blum 6 administered cystin to dogs and rabbits by the mouth, and 

 found it to become oxidised into sulphates. Cystein injected sub- 



1 A. Loewy and C. Neuberg, Zeitschr. f. physiol. Chem. 43. 338 (1904). 



2 Ellinger, Bericht. d. deutsch. chem. Ges. 31. 3183 (1899). 



3 A. Kunkel, Verh. konigl. sacks. Akad. d. Wiss. 27. 344 (1875). 



4 P. Spiro, Arch. f. Physiol. 22. 714 (1890). 



5 G. v. Bergmann, Hofmeislers Beitr. 4. 192 (1903). 6 Blum, ibid. 5. 1 (1903). 



