530 KAHN AND ROSENBLOOM 



sulphur (probably cystin). Cystein similarly injected led to an increase 

 of total sulphur of the urine, the increase being equally divided between 

 inorganic sulphates and neutral sulphur. The authors believe that cystin 

 excreted by subjects of cystinuria has a double source. Perhaps the 

 greater part is from the protein in the diet, that is, exogenous. The other 

 part is endogenous and has no relation to the food. 



One phase of the anomaly of cystinuria appears to consist in the 

 inability to oxidize that part of the sulphur-containing protein which has 

 not been split so far as the cystin stage in the intestine. 



Rothera's experiments in this field are interesting: Cystin prepared 

 by the hydrolysis of hair, as also a specimen of calculus cystin, when 

 given by mouth to man, were completely oxidized to SO 4 and appeared 

 quantitatively as such in the urine. Cholalic acid does not dimmish 

 the excretion of sulphate in the urine, as it might if cystin were a precursor 

 of sulphate, and were converted to taurocholic acid. Cholalic acid given 

 simultaneously with cystin does not interfere with its oxidation to sul- 

 phate. He conclusively established the identity of hair and calculus 

 cystin. His attempts to get the liver to oxidize cystin to sulphate uni- 

 formly failed. 



Magnus-Levy found hydrogen sulphid upon autolysis of liver. He 

 thought that this hydrogen sulphid is derived from the cystein groups of 

 the protein. 



Thiele thought that in cystinuria there is present a defect in the 

 sulphur removing ferments, or in the denitrifying ferments or in both. 



Neuberg recognizes three different types of cystinurics: 



(1) Mild type where there is a tolerance for tyrosin, cystin and 

 asparaginic acid. 



(2) Type in which cystin is excreted and there is present a dimin- 

 ished power to oxidize other amino acids on feeding these amino acids. 



(3) Type in which cases the disturbance of the intermediate protein 

 metabolism is so advanced that besides the excretion of cystin, other amino 

 acids are spontaneously excreted, such as tyrosin, leucin, etc. 



Arnold found that acid extracts of all organs, especially the liver, 

 freed from protein by saturation with Na 2 SO 4 at 34r-37 give the 

 nitroprussid and NH 3 reaction. Liver extract gives also several other 

 reactions characteristic of cystein ; treated with a very little dilute CuSO 4 

 solution gives a fleeting violet color and then a gray precipitate; 

 if this be dissolved by dilute H 2 SO 4 and a drop of 4 per cent sodium 

 nitroprussid be added, immediately a flocculent rusty brown precipitate 

 is formed; with dilute NaOH the cystein copper compound gives a 

 dark violet reaction, which persists for some time. The reactions for 

 cystein disappear slowly when an extract is made alkaline, rapidly when 

 it is treated with H 2 O 2 ; pure cystein solutions show the same behavior. 

 Cystein is a constant and essential constituent of animal cells. 



