522 KAHN AND ROSENBLOOM 



lactis aerogenes, the Bacillus coli communis and the Bacillus acidi lactici 

 in peptone solution containing cystin in suspension, the cystin was decom- 

 posed into either hydrogen sulphid or mercaptan. 



Before we take up the discussion of the metabolic derangement 

 which results in the condition known as cystinuria or cystin calculi, we 

 shall briefly indicate the methods for the detection and separation of 

 cystin from urine. The microscope is a great aid in finding the typical 

 cystin crystals. Patten suggested recognition of cystin by treating the 

 urine with phenyl isocyanate and obtaining the crystals of cystin-phenyl 

 hydantoin acid: 



CHo S S CH 2 

 H | | H 



O = C N CH HC N" C = O 



| ! 



HNC 6 H 5 - C = O O = C C 6 H B N H 



Arnold reported that copper cystin yields a reddish-brown precipitate 

 with a 4 to 5 per cent solution of sodium nitroprussid, and a violet color 

 with a sodium hydrate solution. Upon oxidizing cystin with potassium 

 permanganate, Denis obtained oxalic acid, sulphuric acid, carbon dioxid, 

 acetic acid, nitric acid, ammonia and sulphur. 



The insolubility of cystin in water was called attention to by Wollas- 

 ton and later Briicke laid much stress upon this fact, which, of course, 

 is the explanation for the frequency of cystin calculi in the cystinuric in- 

 dividuals. On account of this insolubility, cystin does not yield a good 

 Siegfried reaction. (Liebermann.) 



According to Neuberg and Ascher cystin when treated with barium 

 nitrate and sulphuric acid is desamidized into 8-oxy-(3-thio-propionic acid. 

 If the cystin is carefully distilled over a free flame the resulting com- 

 pound is diamino-ethylen-disulphid. Mauthner obtained cystin as the 

 copper salt from a patient suffering with cystinuria. By action upon it 

 with zinc dust and lead oxid in ammoniacal solution he obtained alanin. 

 By allowing potassium cyanid to act upon cystin for eight weeks, he 

 obtained l-a-amino-|3-sulfocyanpropionic acid : 



CH 2 CHNH 2 COOH 

 CNS 



Delepine analyzed a sample of urine for Lauder Brunton for cystin, 

 using Lobisch's method. He found that when a specimen was strongly 

 acidified with acetic acid the precipitation took place more slowly than if 

 the specimens were allowed to undergo a spontaneous acid fermentation. 



