THE URINE. 425 



ceed in the following manner : The urine free from albumin is precipitated 

 by basic lead acetate, the lead removed from the filtrate by H 8 S, and concen- 

 trated as much as possible. The residue is extracted with a small quantity of 

 absolute alcohol to remove the urea. The residue is then boiled with faintly- 

 ammoniacal alcohol, filtered, the filtrate evaporated to a small volume and 

 allowed to crystallize. If no tyrosin crystals are obtained then dilute with 

 water, precipitate again with lead acetate, and proceed as before. If tyrosin 

 crystals now separate, they are filtered and the filtrate still further concen- 

 trated to obtain the leucin crystals. 



Cystin, (C 3 H 6 NS0 2 ) 2 . This body is, according to BAUMANK, to 

 be considered as disulphide H ^>C<^^>C<^ H of 



the previously-mentioned cystein, C 3 H 7 NS0 2 (page 393). This last 

 substance, containing sulphur, is considered by BAUMANN as pyro- 

 tartaric acid, whose ketone-oxygen atom is replaced by both the 



monatomic groups NH 2 and SH or ^i|>S<Qg OH . 



BAUMANN and GOLDMAN^ claim that a substance similar to 

 cystin occurs in very small amounts in normal urine. Cystin itself 

 is found with positiveness only, and even then very rarely, in 

 urinary calculi and in pathological urines, from which it may 

 separate as a sediment. Cystinuria occurs oftener in men than in 

 women. Cystin seems to be an abnormal splitting product of the 

 albumins. BAUMANN and v. UDRANSZKY found in urine in 

 cystinuria the two diamins, cadaverin (pentamethylen-diamin) 

 and putrescin (tetramethylen-diamin), which are produced in the 

 putrefaction of albumin (BRIEGER). These two diamins were also 

 found in the contents of the intestine in cystinuria; under other 

 conditions they are not usually present. The author, therefore, 

 considers that some connection exists between the formation of 

 diamins in the intestine by the peculiar putrefaction in cystinuria, 

 and cystinuria itself. Diamins have also been found in the con- 

 tents of the intestines in cystinuria by STADTHAGEN and BRIEGER. 



Cystin crystallizes in thin, colorless, six-sided plates. It is not 

 soluble either in water, alcohol, ether, or acetic acid, but dissolves 

 in mineral acids and oxalic acid. It also dissolves in alkalies and in 

 ammonia, but not in ammonium carbonate. Cystin is optically 

 active and strongly laevo-rotary. If cystin is boiled with caustic 

 alkali it decomposes, yielding among other products alkali sulphides, 

 which may be detected by lead acetate or sodium nitroprusside. On 



