THE NEUTRAL SULPHUR OF THE URINE. 273 



On exposure to the air cystei'n is transformed into cystin, as is 

 shown in the equation : 



CH 3 



| 

 C + H.O 



i 



COOH 



This transformation is of special interest, owing to the fact that 

 under certain conditions cystin also may appear in the urine, while 

 normally it is absent. It is noteworthy, moreover, that cystinuria 

 can scarcely be regarded as a pathological phenomenon, although it 

 may occur in association with a definite disease. More commonly 

 it is observed in otherwise normal individuals, and, like alkaptonuria, 

 it may persist for a lifetime, and may occur in families. It may 

 hence be regarded as a metabolic anomaly in which the oxidation 

 of the loosely combined sulphur is diminished, or perhaps even 

 suspended. Very curiously, it has further been observed that 

 cystinuria is quite constantly accompanied by the appearance of 

 cadaverin in the urine, while in two instances at least putrescin 

 also was found. Some observers have hence suggested that a 

 genetic relationship may exist between the two conditions, and 

 that the formation of the diamins may be the primary factor. But 

 while most observers assume that the diaminuria is referable to 

 the presence of certain specific organisms in the intestinal canal, 

 which are usually absent, I am personally inclined to regard the 

 formation of the diamins also as a metabolic anomaly, and suppose 

 that both conditions are the outcome of a third factor, as yet un- 

 known, but which no doubt operates within the tissues directly. 

 The possible formation of diamins in the absence of micro-organ- 

 isms can indeed no longer be doubted (see page 73). 



The amount of cystin which may be met with in the urine is 

 extremely variable. On some days traces only are found, while on 

 others the elimination may exceed 1 gramme in the twenty-four 

 hours. That the total amount of the neutral sulphur is then also 

 proportionately increased is, of course, self-evident. 



Outside of the urine cystin has been encountered in only a few 

 instances. Cloetta thus claims to have obtained the substance 

 from the kidneys of the ox. Scherer found it once in the liver 

 of a typhoid-fever patient, and Drechsel isolated the body from 

 the liver of a horse and a porpoise. Kiilz further claims to have 

 found cystin among the decomposition-products of fibrin on one 

 occasion where the digestion was effected with pancreas. Together 

 with Dr. Amberg, however, I have been unable to confirm Kiilz's 

 statement in a series of experiments undertaken in my laboratory. 

 Of late, Morner has shown that cystin results on decomposing 

 the keratins of horn shavings with mineral acids. 



Unless the cystin is found directly in a urinary sediment, its pres- 



18 



