The mesobiliviolin reaction and the intermediate products of bilirubin were observed on the B-bile, with the positive Ehrlich's aldehyde reaction, odtained from 20 cases of cholecystopathy, and the results were as follows. 1. After mesobiliviolin reaction on 19 cases the chloroform extract was separated into each pigment by column chromatography, and the absorption curves of each pigment and their changes on the addition of a saturated alcoholic solution of zine acetate were observed. 2. The question whether or not stercoblinogen occupies the position superior to mesobilinogen can be explained by the intensity of bile duct infection, especially the infection by B. coli, or by the intensity of the inflammation findings of bile duct. 3. From the 4 cases treated with antibiotics stercobilinogen could not be detected but only mesobilinogen, suggesting that antibiotics reduce the chemical activity of bacteria. 4. In 4 cases bilirubin and mesobilirubin could be detected and also a pigment that apears to be dihydromesobilirubin. From these results it bas been clarified that the in vivo reduction of bilirubin to urobilinogen is not conducted by liver enzymes but by bacterial enzymes. 5. On 2 cases the detection of d-urobilin was attempted by means of polarimeter and dioxan-HCl boiling method, but the existence of this pigment could not be observed.