Methods have been developed whereby animals can be totally, partially, and intermittently deprived of their bile, without infection of this secretion or of the duct system. In all the instances considered the bile remained sterile throughout the period of the experiment. With this aid we have studied urobilin physiology.

We have been able to show that the normal presence of urobilin in the bile and feces of dogs depends on the passage of bile pigment to the intestine, either through the normal channels, or by abnormal ones, as when it is fed by mouth. Complete loss of the bile from the body resulted in the total disappearance of urobilin and urobilinogen from the bile, feces, and urine. Rarely very faint traces remained in the feces, the origin of which has been discussed. Partial loss of the bile resulted in a corresponding reduction in the urobilin of the dejecta.

Feedings of sterile urobilin-free dog bile to intubated dogs losing all of their bile and having no urobilin in it, or in feces or urine, were followed by the appearance of the pigment in the hepatic bile secreted shortly thereafter. When the feedings were stopped the urobilin soon disappeared.

Total obstruction of the bile flow caused disappearance of the urobilin of the bile and stool. Later as the animals became heavily jaundiced the pigment appeared again in very small quantity in the feces. Autopsy at this time showed that the intestinal mucosa was deeply tinted with bilirubin some of which undoubtedly had passed into the lumen of the bowel and had there been changed to urobilin.

Employment of the "altercursive intubation," by which an intermittent diversion of the bile stream of animals from the intestine to a collecting apparatus could be effected, showed that while bile pigment still reached the intestine urobilin was present in the bile secreted by the liver but that almost at once after the bile had been diverted from the gut urobilin disappeared from it. In relation to this finding it was noticed that in animals from which merely a small fraction of the bile was collected, that from a single liver lobe, while the greater portion reached the intestine there was most urobilin in the bile at times when most bilirubin was entering the intestine.

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