The jaundice that develops after obstruction of the common duct in the absence of complications, expresses the physiological wastage of corpuscles occurring from day to day; and the intensity of the bilirubinemia varies as does the total of functioning hemoglobin-containing tissue from which this wastage takes place. There is to be observed a constantly readjusted direct relationship between hemoglobin percentage, bilirubinemia, and, by corollary, bilirubinuria. Induced losses of red cells find expression at once in a lessened accumulation and excretion of bile pigment; and as the regeneration of hemoglobin takes place the amount of bile pigment increases pari passu both in plasma and urine. The jaundice of bile retention is far less pronounced during secondary anemia than when the individual is full blooded, other things being equal. During uncomplicated obstructive jaundice the intercurrent changes in bilirubinemia correspond closely with those in circulating hemoglobin even when tissue icterus is of long standing. The fact indicates the presence of a barrier to the distribution of bile pigment from the blood, and such a barrier is to be found in the walls of the vessels. Its influence is at once evident on comparing lymph specimens and blood specimens from the long jaundiced animal. The amount of bile pigment in the lymph is then seen to be negligible, relatively speaking. Tissue icterus should be thought of as, ordinarily, the highly imperfect secondary expression of a condition which tends to be localized to the blood pool. On occasion more pigment than usual may escape from this pool, as for example into the wheats of the yellow urticaria described by clinicians.
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