FURTHER FATE OF AMINO ACIDS 117 



slight solubility is deposited as hexagonal crystals. It 

 may also form cystine concretions in the bladder. The 

 condition of cystinuria with that of alkaptonuria must 

 be regarded as an anomaly of metabolism. Cystinuria 

 appears to be a distinctly hereditary condition since 

 it may appear in families for many generations, and 

 apparently follows the Mendelian law of heredity. 

 Like alkaptonuria it is found oftener in males than in 

 females ; it seems to lead to no pathological symptoms 

 other than the formation of concretions. There is 

 probably no complete failure to destroy cystine since 

 only a portion of the cystine from protein ingested 

 reappears in the urine. Undoubtedly a part of the 

 cystine is catabolized in a normal manner. From the 

 fact that cystinuria persists in the absence of protein 

 intake and further that cystine fed to cystinurics fails 

 to appear in the urine, the conclusion may be reached 

 that the urinary cystine has its origin in that formed 

 during catabolism of the tissues. It may be possible 

 that in these subjects there is only a limited capacity 

 for destroying amino acids in general for, in addition 

 to cystine, leucine and tyrosine have been found in 

 some cases. 



At times the diamines cadaverine and putrescine 

 formed by putrefaction in the intestine may also be 

 present in the urine of cystinurics. The diamines are 

 significant in that they are two of the so-called 

 ptomaines. Putrescine and cadaverine occur also in 

 diseased conditions of the intestinal tract, thus they 

 may be found in various infections, in cholera, dysen- 



