INFECTIONS OF THE DIGESTIVE TRACT 65 



with the contents of the digestive tract in adults that a 

 strong red coloration with this aldehyde is commonly 

 obtained in persons in fair health and that a moderate 

 reaction is usual in persons who are well. The reaction 

 depends in part on the presence of indol and perhaps in 

 part also on the presence of urobilinogen. In the case 

 of a bottle-fed child, there is usually only a faint pink 

 tinge when the conditions of the reaction are such as will 

 give a distinct red in the case of material from adults. 

 On standing, however, for several days, a blue-gray 

 coloration may set in, the nature of which is not at 

 present clear. 



If we acidify a watery suspension made from any por- 

 tion of the contents of the intestinal tract, we find that a 

 moderate amount of volatile acid is obtained in the dis- 

 tillate. The molecular weight of such acids lies usually 

 between sixty and sixty-five; that is to say, it corre- 

 sponds closely to the molecular weight for acetic acid. 

 There is no doubt that acetic acid forms by far the larger 

 amount of the acids normally present in the distillate 

 prepared as just mentioned. The presence of acetic acid 

 rather than of higher fatty acids indicates that such 

 bacterial processes of decomposition as occur within the 

 intestinal tract are of a fermentative rather than of a 

 putrefactive nature. It is a fact of interest that if we 

 take the intestinal contents of a normal horse and make 

 a distillation for the determination of the volatile acids 

 present, this volatile acid also corresponds in molecular 

 weight to the figures corresponding to acetic acid. The 

 same thing is true of young pigs. These facts, and others 



