CHR. BARTHEL 



that it is of no consequence whether this compound is present 

 or not. To be sure, in some cases the growth (turbidity) was 

 stronger in the tubes which also contain ammonium lactate, 

 but examples to the contrary are also to be noted, and in no 



TABLE 2 



cases has the indol reaction given different results in the tubes 

 with and without ammonium lactate. 



The results of the experiments here related are that the solu- 

 tion of Zipfel is equally satisfactory even without ammonium 

 lactate, but that under all conditions it must be neutralized.* 



^ It may happen occasionally that the tryptophane solution gives satisfactory' 

 results without neutralization, but this probably generally depends upon an 

 especially strong leaching of the alkali from the glass during the sterilisation. 



