288 THE URINE. 



This product they subsequently identified as brom-phenyl cys- 

 tei'n, and the proof had thus been furnished that a cystin com- 

 plex is normally produced in the sulphur metabolism of the 

 dog, at any rate. It is identical with the cystei'n which can be 

 obtained from the albuminous cystin on reduction, and the elimina- 

 tion of mercapturic acid can hence be regarded as an experimental 

 cystin uria. 



The amount of cystei'n which is normally present in the urine 

 probably does not exceed 0.015 gramme in the twenty-four hours. 

 Larger quantities are found under pathological conditions, as in 

 phosphorus poisoning, but on the whole its elimination in disease 

 has received little attention. 



Cystin. As has been shown, cystin is a constant decomposition- 

 product of all albumins and represents one of the primary radicles 

 of the original molecule. Under normal conditions it is not found 

 in the urine. As in the case of alkapton, its presence represents 

 the existence of a distinct metabolic anomaly, of the true nature of 

 which, however, nothing is known. Very curiously its presence in 

 the urine may be associated with the simultaneous presence of cer- 

 tain diamins, viz., cadaverin and putrescin. As these were formerly 

 regarded as specific products of bacterial activity, their presence 

 was brought into a supposed causal relationship to that of cystinuria. 

 In the light of more modern investigations, however, we may assume 

 that the diaminuria in these cases is in all likelihood also the expres- 

 sion of a metabolic anomaly, and like the cystinuria of histogenic 

 origin. 



Outside of the urine cystin has been encountered, as such, in a 

 few instances only. Cloetta claims to have found it in the kidneys 

 of the ox, Scherer in the liver of a patient dead with typhoid fever, 

 and Drechsel isolated the body from the liver of a horse and a 

 porpoise. Abderhalden has described the case of a child which died 

 at the age of twenty-one months and a half, and in which post 

 mortem the various organs, and notably the liver and spleen, were 

 found incrustated with cystin crystals. 



Clinically cystin is of interest as its elimination in the urine 

 favors the formation of cystin concretions. 



The amount which may be met with is extremely variable. On 

 some days traces only are found, while on others the elimination 

 may amount to a gramme or more. The neutral sulphur is corre- 

 spondingly increased (to 60 per cent, of the total and even higher). 

 Very commonly the cystin separates out in crystals shortly after 

 being voided, but sometimes it is necessary to acidify the urine 

 strongly with an excess of acetic acid. On decomposition such 

 urines develop a strong odor of hydrogen sulphide. 



Properties. Structurally cystin is -diamido-/9-dithio-dilactic 

 acid; it is the disulphide of /9-cystei'n and results from this on 

 oxidation according to the equation : 



