SUGAR IN THE NUTRIENT MEDIUM. 139 



as a function of the nascent hydrogen which the bac- 

 teria produce, i.e., they regard the formation of H 2 S 

 as a proof of the formation of nascent hydrogen. 



3. Thiosulphate and thiosulphite. This has been 

 studied especially in yeast but has also been demon- 

 strated in the case of some bacteria (by Petri and 

 Maassen) . 



4. Sulphates. Beyerinck in particular has de- 

 monstrated this practically important function for his 

 (morphologically poorly characterized) motile, strict 

 anaerobic spirillum desulphuricans. It is rarely 

 found developed among other bacteria (C. B., Part 

 II. , Vol. L, 1). 



Rubner has shown that in bacterium vulgare the 

 decomposed organic sulphur always suffices for the 

 production of sulphuretted hydrogen. 



The presence of sugar in the nutrient media rarely 

 prevents or diminishes the production of sulphur- 

 etted hydrogen, even when the bacteria are able to 

 decompose (ferment) sugar vigorously. The decom- 

 position of hydrocarbons does not protect the albumi- 

 noids from decomposition. The presence of saltpetre 

 is a disturbing factor and under these circumstances 

 very little H 2 S but an abundance of nitrite is formed 

 (Petri and Maassen). The exclusion of oxygen favors 

 the production of sulphuretted hydrogen. On pass- 

 ing air through the cultures of facultative anaerobic 

 producers of sulphuretted hydrogen the amount of 

 H 2 S produced diminishes considerably, and in its 

 place sulphates are formed. 



Many producers of sulphuretted hydrogen also 

 produce stinking mercaptan (CH 3 SH), demonstra- 

 ble by the green color which it gives to the yellow- 



