242 INFECTIONS OF THE DIGESTIVE TRACT 



cians that persons in whom a very strong indican reac- 

 tion can be obtained in the urine during a long period 

 of time invariably suffer from nervous or dyspeptic dis- 

 orders, and many careful physicians have believed that 

 there is some causal connection between the absorption 

 of indol from the intestine and the development of func- 

 tional nervous or nutritional derangements. I believe 

 that in recent years the grounds for this conviction have 

 been considerably strengthened. Nevertheless, it can 

 hardly be said that the relation between the absorption 

 of indol and the symptoms of intoxication in man has 

 ever been placed upon a firm scientific basis. I believe 

 that I have myself underestimated the importance of 

 indol as a toxic agent in man, and desire to present here 

 evidence which has lately come to light in regard to the 

 influence of indol on the animal organism. For this rea- 

 son I shall discuss the subject of indol poisoning some- 

 what fully. 



Indol is not a product of the tryptic digestion of proteids, 

 and probably cannot be formed in the course of physio- 

 logical processes without the intervention of organized 

 ferments such as bacteria. In the human intestine the 

 presence of indol is dependent on the action of living 

 bacteria, although it is likely that the action of the diges- 

 tive juices may prepare the way for the attack of bacteria 

 on proteid material. The indol produced in the intes- 

 tine is, like skatol, dependent on the production of a 

 more complex substance known as tryptophan. A very 

 careful study of the chemical constitution of tryptophan 

 was lately made by Gowland Hopkins of Cambridge 



