PRODUCTION OF HYDROGEN SULPHIDE 245 



acids than the American products. It probably also has a higher 

 percentage of sulphur bearing constituents, possibly cystin. 

 It would be interesting to determine the relative amounts of 

 cystin in each type of peptone, but this has not yet been done. 

 A series of experiments was carried out to study the effect of 

 various carbohydrates on hydrogen sulphide formation, by B. 

 paratyphosus B. A medium made up of 3 per cent. Witte pep- 

 tone, 0.5 per cent NaCl and 0.5 per cent of the carbohydrate 

 was used. It was sterilized for twenty minutes in the Arnold 

 on three consecutive days. Three monosaccharides, glucose, 

 levulose and galactose; two disaccharides, lactose and sucrose; 

 and a glucoside salicin were tried. No marked constant effect 

 of these different carbohydrates on hydrogen sulphide formation 

 was noted; this is not quite in accord with the observations of 

 Seifert (1909) who found that the presence of glucose and lactose 

 in peptone media decreased the amount of hydrogen sulphide 

 formed. 



Hydrogen sulphide production by B. Paratyphosus A and B. 

 Paratyphosus B. and B. typhosus and B. dysenteriae 



A number of strains of B. paratyphosus A, B. paratyphosus 

 B. B. typhosus, and B. dysenteriae, were procured. Some of the 

 cultures were obtained from the University of Chicago, some from 

 the University of Kansas, some from the American Museum of 

 Natural History, New York City, and some were freshly isolated 

 from blood or stools at the University of Nebraska, College of 

 Medicine. Their power of producing hydrogen sulphide was 

 tested in a 3 per cent solution of Witte's peptone containing 0.5 

 per cent of NaCl, the same medium made from Difco and from 

 Fairchild's peptones, respectively, and broth prepared from 

 Difco peptone. All media were sterilized in the Arnold. The 

 results are recorded in tables 5 and 6. 



The tables need but little comment. So far as the cultures 

 investigated were concerned B. typhosus always produced large 

 amounts of hydrogen sulphide in twenty-four hours or less, while 



