144 INFECTIONS OF THE DIGESTIVE TRACT 



to the skatol employed in making the standard color 

 solution. This then imparts to the standard color solu- 

 tion a violet tint like that obtained from the distillate 

 to be matched. It seems unnecessary to give further 

 details. After some experience with the method of match- 

 ing colors it is possible to employ the method so that it 

 will give satisfactory quantitative results. 



It is not desirable here to enter into a description of 

 the chemical methods of studying the f seces and the urine. 

 The methods ordinarily employed for this purpose are 

 fully described in text-books relating to these subjects. 

 It may be stated, however, that numerous observations 

 have been made upon the acids and bases present in 

 human fseces in health and disease and the intestinal 

 contents have been studied for hydrogen sulphide and for 

 the presence of mercaptan. The reaction of the fseces 

 with concentrated solution of mercuric chloride, accord- 

 ing to the manner first described by Schmidt, 1 is of much 

 value in determining the presence of a substance sup- 

 posed to be hydrobilirubin. The marked red color 

 with yellowish fluorescence which is a characteristic of 

 Schmidt's reaction is supposed to depend on the oc- 

 currence of a combination between the mercuric salt 

 and hydrobilirubin. An analogous combination exists 

 in Jaffe's zinc-chloride-urobilin compound. Both sub- 

 stances give the same spectroscopic picture; namely, 

 a band between the lines b and E. An intensification 

 of the red color obtained in the Schmidt reaction may 

 often be secured by transferring a portion of the tested 



1 " Verhandl. d. Congresses f . inn. Medicin," xiii, p. 320, 1895. 



