SULPHUR-CONTAINING SUBSTANCES 477 



has also been detected in the contents of the gastro-intestinal 

 tract. 



Apparently these substances are absent from normal feces, 

 but this does not exclude the possibility of their normal forma- 

 tion, absorption, and destruction. There is no evidence that 

 they ever cause symptoms or pathological alterations. 



(3) SUBSTANCES ARISING FROM THE SULPHUR-CONTAINING 

 RADICAL OF THE PROTEID 



Most if not all of the sulphur in the proteid molecule seems 

 to be contained in the amino-acid, cystin, which has the 

 following composition : 



g _ CH 2 CHNH 2 COOH 

 S _ CH 2 CHNH 2 COOH. 



From this is formed the hydrogen sulphide of the intestinal 

 gases, of which about 0.058-0.066 gram is present in each 

 one hundred grams of normal colon contents. Although 

 Senator has described a case in which an intoxication with H 2 S 

 of intestinal origin occurred, this gas seems not to be a frequent 

 cause of intoxication, and Senator's case stands almost alone. 

 Under normal conditions H 2 S does not appear in the urine, any 

 that may be absorbed probably being oxidized to SO 4 . If 

 enough H 2 S should enter the blood so that it was not completely 

 destroyed, it might well cause harm, for it is decidedly toxic, 

 particularly affecting the nervous system ; but we have no 

 evidence that this often happens. Van der Bergh l has observed 

 cases of intestinal obstruction in which the presence of sulphemo- 

 globin in the patient's blood was demonstrated. 



Methyl mercaptan, CH 3 SH, has also been found in the feces, 

 although it seems not to be abundantly or constantly present, 

 according to Herter, 2 who found also that mixed bacteria from 

 normal feces rarely produce mercaptan in cultures. However, 

 bacteria from the feces of persons suffering with various diseases 

 often produce mercaptan. Ethyl mercaptan, C 2 H 5 SH, and ethyl 

 sulphide, C 2 H 5 S C 2 H. , have also been described as fecal 

 constituents. It is not known that the mercaptans are a cause 

 of intoxication. 



1 Deut. Arch. klin. Med., 1905 (83), 86. 



2 Jour. Biol. Chem., 1906 (1), 421. 



