520 KAHN AND ROSENBLOOM 



In the feathers of the goose, Buchthala found 6.3 per cent. He also 

 analyzed the egg membranes of the Scyllium stellare and obtained 0.44 

 per cent cystin; of the Pristiurus melanostomis and obtained 0.60 per 

 cent ; of the Scyllium canicula and obtained 0.42 per cent. But attention 

 is to be called to the fact that in the last three analyses Buchthala did 

 not isolate the cystin, but determined the sulphur and computed the amount 

 of cystin from the amount of sulphur present. 



Cystin occurs rarely in human bladder concretions. It is more fre- 

 quently present in the urine and calculi of dogs. In human urine it 

 occurs in cases of cystinuria. Cloetta found cystin in cow's kidneys 

 (1856). Scherer found it in the liver of a drunkard who died from 

 typhoid fever, and Drechsel found it constantly together with the xanthin 

 bases in the horse's liver. Magnus-Levy found H 2 S upon autolysis of 

 the liver which he states is derived from the sulphur of the cystin groups. 

 In the protein of yeast, Schroder found 0.72 per cent sulphur. He boiled 

 the protein for several hours with 12.0 per cent hydrochloric acid, and 

 found that cystin -was one of the products of hydrolysis. Arnold made 

 extracts of liver, thymus, muscle, heart, brain, testicles, kidneys, in- 

 testines, lens and spleen, and he found that all the extracts that were 

 protein-free contained cystin. He found most in the liver and spleen. 

 Keis found cystin by the Arnold reaction only in normal eye lens ; lenses 

 which had undergone cataract formation did not give this reaction. Win- 

 terstein and Strickler found 0.05 per cent cystin in colostrum of milk. 

 Drechsel found cystin in the liver. Baumann and Goldmann reported 

 that cystin was present in normal urine, but Stadthagen(a) refuted this. 

 Hofmann stated that cystin is present in the sweat of cystinuric pa- 

 tients. 



In 1890, Kulz found that when he permitted 290 gm. fibrin, 270 

 gm. ox pancreas, 3 gm. salicylic acid and 1 liter water to stand at room 

 temperature for fourteen hours, he could isolate cystin. That cystin is 

 one of the products of peptic digestion of protein was demonstrated by 

 Lang-stein, who isolated this sulphur compound, together with other ammo 

 acids after protein digestion. 



In 1869, Maly attempted the synthesis of cystin, but he was unsuc- 

 cessful. He tried to condense a watery solution of aldehyd-ammonia, 

 potassium sulphocyanate and hydrochloric acid. The resultant product 

 was "cystin-like," but not cystin. 



In 1903, Erlenmeyer, junior, reported the synthesis of cystin, and 

 one year later in collaboration with Stoop, he gave a detailed description 

 of his method. The stages in the synthesis are first benzoylserin which 

 upon being heated with phosphorus pentasulphid produced benzoylcystein. 

 Upon hydrolysis this yielded cystein, which upon oxidation lost hydrogen 

 and changed to cystin : 



