INFECTIONS OF THE DIGESTIVE TRACT 229 



formed in other parts of the digestive tract. There are 

 cases of dilatation of the stomach from which one may 

 remove material which is undergoing putrefaction with 

 the formation of hydrogen sulphide. The production 

 of hydrogen sulphide in this situation is certainly to be 

 regarded as pathological. I am not clear, however, that 

 it points to the presence of pathological bacteria, for 

 it is easy to show that typical organisms of the B. lactis 

 aerogenes type are able to form hydrogen sulphide when 

 growing in bouillon containing cystin. Cystin is a decom- 

 position product of proteids, and it is conceivable that in 

 a stagnant stomach proteid digestion may go on to the 

 formation of cystin among the cleavage products and that 

 this is then decomposed through the action of B. lactis 

 aerogenes. The ability to form hydrogen sulphide from 

 cystin is widespread among bacteria. The colon bacilli 

 liberate it abundantly when growing in a cystin medium. 1 



Among persons who take organic iron it is usual to 

 note, after a little time, a dark brown color on the tongue 

 which appears to be dependent on the formation of iron 

 sulphide in this situation. The sulphide production 

 is referable, doubtless, to the formation of hydrogen 

 sulphide, but the conditions of its production are not 

 I known. It does not appear that the blackening of the 

 , tongue after taking iron can be regarded as pathological, 

 |as it may be observed in persons apparently free from 

 i disorders of digestion. 



I have made some observations to determine at what 



1 This is true also of the bacilli of dysentery and of typhoid 

 fever. 



